s 


'    c< 


:<r  <-<-  <^«k 


>« 


rr 


<^r 


George  Washington  Flowers 
A  iemorial  Collection 

Dl  KK  UNIVERSITY  LIBRARY 


ESTABLISHED   BY  THE 
FAMILY  OF 

COLONEL   FLOWERS 


— w — 

• 

O 

g 
O 

• 

W 

0 

» 
>> 

03 

I 

O 

0) 

o 

• 

(/) 

*H 

tf 

rH 

rH 

•H 

* 

KJ 

i 

• 

0 

• 

3 

rH 

i 

0 
0 

CO 

• 

o 
■♦-> 

03 

■H 

O 

o 

V) 

• 

S 

I 

A 

h- 

Q 

-J 

^ 

UJ 

u 

0 

* 

Li 

_j 

o 
o 

2 

< 

-J 

Q. 

Q 

Z 
CM 

J 

0 

0) 
0 

o 

* 

Q 
< 

2 

o 
o 

CvJ 

Ul 

u 
u 

0 

DO 

o 

10 

SUMMARY 


COIUSE  OF  PEBJAMXT  FORTIFKATIOX 


AXP    OF    THF. 


[ttark  attb  §ifmtt  «l  permanent  P»tb, 


FOR    THF.    USE    OF    THE 


cadets  of  the  u.  s.  MILITARY  ACADEMY. 
BY  D.  H.  MAHAN, 

PROFESSOR    OF    MILITARY    ENGINEERING.    ETC.,    ETC. 


EMTION    PRESENTED    TO    WAR    DETARTMFNT,    C.    S.    A., 

BY  COL.   BLANTON  DUNCAN. 


COLUMBIA,    S.    C.  : 
IOUTB     CAROLINIAN     |TBAM*POWKB     J: 

Ift 


TABLE  OF  CONTENTS. 


PA  OB 

System  of  Fortification  Drawing ."> 

Permanent  Fortification ;53 

Component  Elements  of  Permanent  Works ::i 

OrEN  Defences 4'» 

Covered  Defences 50 

Communications 67 

Elements  of  the  Plan  of  Enceintes  and  Outworks 71 

Outworks  am>  Detached  Works 7:; 

Interior  Retrenchments 7s 

I !  A  STIONEI)    S Y STEM  S ~[ I 

Vauban's  1st  Method 81 

\  ai  ban's  3d  Method 88 

Cormontaingne's  Method '»•_> 

Methods  of  the  Schools  of  Mezieres  and  Metz 99 

v   /!  B*a  Method ' 101 

Cha8SBL01  i-'s  Method 1  \\\ 

Haxo's  Method i:,:; 

Choumara's  Method 157 

Coehorn's  Method 166 

T<  \  aiu.fi>    SYSTEM 172 

< 'a knot's  Tenatlled  Method 17:; 

Polygonal  System 171; 

MONTALEMBI  RT's    POLYGONAL    METHOD    17s 

i:  ».<  i  \  i  German  Fortifications lg] 

Fronts  pi  Posen l!tn 

i  ndeb in:; 

Wore  at  Grrmersheim [96 

Ian  Ports *202 

Adaptation    "i    Permanent    Fortification   to  the    l 

ORAPHYOA]     FEATURES    Of    FRONTIERS 204 

\  oi  the  Pr<  Fortification   

PRO<  1      [111      l\\  KNTION    <•(     I    IRKAP.M- 

Inm  r  Irreoui 

Mines  

lck  and  Defence  of  ] 


SUMMARY        • 

OF   THE 

COURSE  OF  PERMANENT  FORTIFICATIONS 

ANT)  OF  TITE 

ATTACK  A\0  DEFEXCE  OF  PERMANENT  WORKS. 


SYSTEM  OF  FORTIFICATION  DRAWING. 


I. ..The  method  now  in  general  use,  among  military  engi- 
neers, for  flclinoat ijilt  the  plans  of  permanent  fortifications,  is 
similar  to  the  one  which  had  been  previously  employed  tor 
representing  the  natural  surface  of  ground  in  topographical 
ami  hydrographical  surveys;  which  consists  in  projecting,  on 
a  horizontal  plana,  a)  any  assumed  level,  the  bounding  lines 
of  the  surfaces  ami.  also,  the  horizontal  line-  ent  from  them  by 
equidistant  horizontal  planes ;  the  disti  these  lines  from 

the  Mil  mad  plane  I  numerically  in  U  rms  of 

linear  measure,  as  a  yard,  a  I 

2...P  lu  r?  1:1  \<  i .   i 

horizontal  plane,  apon  which  the  linei  are  project)  med 

the  .  it  ip  the  < 

to  which  th-  g  of  all  I  i  it  arc  ;  .  and 


"I     I  <  >Kl  11  1<  .VI  K'.\    DRAWING. 

as  il  irapare  these  distances  ^i^i  each  other,  and  to 

•  nnine  the  relative  positions  of  the  lines. 

::...]:  •■)-.    The  numbers  which  express  the  distances 

from  the  plane  of  comparison,  are  termed  refer- 

The   unit   in  which  these  distances  are  expressed,  is 

usually  the  Linear  foot  and  it-  decimal  divisions, 

the  position  assumed  For  the  plane  <>t'  comparison* is  arbi- 
trary, it  may  betaken  either-above  or  below  every  point  of 
the  surface  to  be  projected. 

In  the  French  military  service,  it  is  usually  taken  above; 
in  our  own,  below  tin-  surface.  The  latter  seems  the  more 
natural  ami  is  more  convenient,  as  vertical  distances  are  more 
habitually  estimated  from  below  upward  than  in  the  contrary 
direction.  Each  of  these  methods  has  the  advantage  of  re? 
quiring  but  one  kind  of  symbol  to  be  used,  viz:  the  numerals 
expressing  the  references;  whereas,  if  the  plane  of  comparison 
were  bo  taken  that  some  of  the  lines  projected  should  lie  on 
-i«le  of  it  and  some  on  the  other,  then  it  would  he  neces- 
sary to  use,  in  connection  with  the  references,  the  algebraic 
Bymbols  plus  or  mirvu8%  to  designate  those  lines  above  the  plaae 
from  those  below  it. 

This  method  of  representing  objects  has^iven  rise  to  a  very 
useful  modification  of  the  ordinary  one  of  orthogonal  projec- 
tions on  two  planes,  and  has  been  denominated  one  j>/<t//e 
iptvoi  geometry }  the  plane  of  comparison  being  the  sole 
plane  of  projection;  the  references  taking  the  place  of  the 
usual  projections  on  a  vertical  plane.  By  this  modification'^ 
the  number  of  lines  to  be  drawn  is  greatly  decreased;  the 
plication  of  the  drawing  lessened;  the  graphical  operations 
required  in  die  solution  of  problems,  presented  by  the  drawing, 
simplified ;  and  the  relations  of  the  parts  more  readily  seized 
upon,  as  the  eye  is  confined  to  one  plane  of  projection  alone. 
Bui  the  chief  advantage  of  it  consists  in  .its  application  to  the 
delineation  of  objects,  like  works  of  permanent  fortification, 
where,  from  the  ureal  disparity  of  the  horizontal  extent 
eov<  red,  and   the  vertical   dimensions  of  the  part s,  a  drawing, 


SYSTEM   OF   FORTIFICATION    DRAWING.  7 

made  to  a  scale  which  would  give  the  horizontal  distances 
with  accuracy,  eould  not  in  most  cases,  render  the  vertical 
dimensions  with  any  approach  to  the  same  degree  of  accuracy  ; 
or,  if  made  to  a  scale  which  would  admit  of  the  vertical 
dimensions  being  accurately  determined,  would  require  an  area 
of  drawing  surface,  to  render  the  horizontal  dimensions  to  the 
same  scale,  which  would  exceed  the  convenient  limits  of  prac- 
tice. 

Taking,  for  example,  an  ordinary  scale  used  for  drawing  the 
plans  of  permanent  fortifications  of  one  inch  to  fifty  feet,  or 
the  scale  1-600,  the  details  of  all  the  hounding  surfaces  can  be 
determined  with  accuracy  to  within  the  fractional  part  of  a 
foot;  whereas,  a  vertical  projection  to  the  same  scale  would 
be  altogether  too  small  for  the  same  purpo 

The  reference  of  any  point  or  line  of  the  plane  of  reference 
will,  therefore,  be  zero';  that  of  any  point  above  it  will  be  ex- 
pressed in  feet,  decimal  parts  of  afoot  being  used  whenever 
the  reference  is  not  an  entire  number.  In  writing  the  refer- 
ence the  mark  used  to  designate  the  linear  unit  is  omitted,  in 
korder  that  the  numbers  expressing  references  may  not  be  mis- 
taken for  those  which  may  be  put  upon  the  drawing  to  express 
the  horizontal  distances  between  points. 

The  references  of  horizontal  lines  are  written  upon  the  pro- 
jections of  these  lines.  All  other  references  are  written,  as 
nearly  as  practicable,  parallel  to  the  bottom  border  of  the 
drawing,  for  the  convenience  of  reading  them  without  having 
ti  shift  the  position  of  the  sheet  on  which  the  drawing  is 
made. 

4.,.Poon  \m>  Right  Link.    To  designate  the  position  of  a 
point,  PI.  1,  Fig.  1,  the  projection  of  the  point  ami   it 
ence   are   enclosed  within   a   bracket,  thu  I).      This   e\- 

prcoaes  that  the  vertical  distance  of  the  point  from  the  plane 
of  reference  is  88  feet  and  50-100  of  a  toot.  The  position  of  a 
right  line,  oblique  to  the  plane  of  re:  nated  by 

the  projection  of  the  lino,  and  the  references  of  any  two  of  its 

points.      Thus,  in    Fig.  1.  the   points  ./  and  t>.  upon   the   projec 


s  !  ..Kill -li-ATli'N    DRAWS*}. 

ti..n  of  tin-  right  line,  with  their  respective  references,  (25,15) 
and  determine  the  position  of  the'  line  with  respect  to 

the  plane  of  referenc 

When  the  line  is  horizontal,  or  parallel  to  the  plane  of  refer- 
.  its  projection,  with  the  reference  of  one  of  its  points,  will 
be  sufficient  to  designate  it,  and  fix  its  position  with  respect  to 
tin-  plane  of  reference.  Thus,  in  Fig.  1,  the  reference  (25,15) 
written  upon  the  projection  of  the  line,  expresses  that  the  line 
tg  horizontal,  and  B5,15  feet  from  the  plane  of  reference. 

5...Fof  the  convenience  of  numerical  calculation,  the  posi- 
tion of  a  line,  with  respect  to  the  plane  of  reference,  is  often 
expressed  in  terms  of  the  natural  tangent  of  the  angle  it  makes 
with  the  plane:  bul  as  this  angle  is  the  same  as  that  between 
the  line  and  its  projection,  its  natural  tangent  can  be  expressed 
by  tin-  difference  of  level  between  any  two  points  of  the  line, 
divided  by  the  horizontal  distance  between  the  points.  Now, 
as  the  difference  of  level  between  any  two  points  of  the  line  is 
the  Bame  as  the  difference  of  the  references  of  the  points,  and 
the  horizontal  distance  between  them  is  the  same  as  the  hori- 
zontal projection  of  the  portion  of  the  line  between  the  same, 
points,  it  follows,  that  the  natural  tangent  of  the  angle  which 
the  line  makes  with  the  plane  of  reference  is  found  by  dividing 
the  difference  of  the  references  of  the  points  by  the  distance 
in  horizontal  projection  between  them. 

The  vulgar  fraction  which  expresses  this  tangent  is  termed 
the  inclination,  ot  deolimfry  of  the  line.  Thus,  the  fraction 
1-t;  would  express  that  the  horizontal  distance  between  any 
two  points  is  six  times  the  vertical  distance  or  difference  of 
their  reference.-:  the  fraction  -$,  that  the  vertical  distance  be- 
tween anv  two  points  i^  two-thirds  of  the  horizontal  distance; 
tin  denominator  of  th*  fraction^  in  all  cases,  representing  the 
number  of  parts  in  horizontal  projection,  and  the  numerator 
tic  >;,/■,■■  gtpondmg  n  utnit  ,•  of  parts  in  vertical  distance. 

When  the  position  of  a  line  is  designated  in  this  way,  it  is 

to   he  a  line  whose   inclination,  or  declivity,  is  one-sixth, 

two-thirds,  ten   on  one,  etc.,  or  simply  a  line  of  one-sixth,  etc. 


SYSTEM   OF   FORTIFICATION    DRAWING.  9 

f>..."When  the  projection  of  a  line  is  divided  into  equal 
parts,  each  of  which  corresponds  to  a  unit  in  vertical  distance, 
and  the  reference  of  the  points  of  division  arc  written,  it  is 
termed  the  scale  of  declivity  of  the  Inn .  In  constructing  the 
scale  of  declivity  of  a  line,  the  entire,  references  arc  alone  put 
down  ;  one  of  the  divisions  of  the  equal  parts  being  subdi- 
vided into  tenths,  or  hundredths  if  necessary,  so  as  to  give  the 
fractional  parts  of  the  references  corresponding  to  any  frac- 
tional part  of  an  entire  division. 

7...  I  laving  the  inclination  of  a  line,  the  difference  of  n  fer- 
ence  of  any  two  of  its  points,  the  projections  of  which  are 
given,  will  be  found  by  multiplying  the  horizontal  distance  be- 
tween them  by  the  fraction  which  expresses  this  inclination  ; 
in  like  manner,  the  horizontal  distance  of  any  two  points  will 
be  obtained  by  dividing  the  difference  of  their  references  by 
this  fraction. 

To  obtain,  therefore,  the  reference  of  a  point  of  a  line,  hav- 
ing its  projection,  the  horizontal  distance  between  it  atid  that 
of  some  other  known  point  of  the  line  must  be  determined, 
from  the  scale  of  the  drawing  by  which  the  horizontal  dis- 
tances are  measured  ;  this  distance  expressed  in  numbers,  be- 
ing multiplied  by  the  fraction  which  expresses  the  inclination 
of  the  line,  will  give  the  difference  of  reference  of  the  two 
points  ;  the  required  reference  of  the  point  will  be  found  by 
subtracting  this  product  from  the  reference  of  the  known 
point,  if  it  is  higher  than  the  one  sought,  or  adding  if  it  is 
lower.  Thus,  Let  (25,15)  be  the  reference  of  a  known  point 
higher  than  the  one  sought ;  the  distance  between  the  points 
being  85,57  feet,  and  the  inclination  of  the  line  1-10 ;  then, 
...  ■  l-l"  8,575  will  be  the  difference  of  reference  of  the 
points,  and25,15-  8,575  21,575,  the  required  reference.  The 
converse  of  this  show.-  that  the  horizontal  distance  between  two 
points  on  this  line,  who.-'-  difference  of  reference  is  3,57*5,  will 

be  3,575-j-l-10=85.75  feet 

< 

The   true    length  of  any    portion  of  a   line    between    two 
-idently  the    hype .t he'iii.--  of  I  light-angle  tri- 

a 


LO  •"    «>l-     FORTIFICATION    I'KAWIN... 

ther  two  Bides  are  the  difference  of  refer- 

,(1  tluir  horizontal  distant 

•  '..M  of  a  plane  Dbliqne  to  the  plane  of 

.  may  be  determined  tit  ln-r  by  the  projections  and  ref* 

bE  points  ;  by  the  projections  and  declivity 

in  it  oblique  to  the  plane  of  reference  :  or  by  the 

•  two  or  more  horizontal  lines  of  the  plane,  with 

more  usual  method  of  representing  a  plane  is  by  the 

proj  n  the  plane  of  reference  of  the  horizontal   linea 

rmined  by  intersecting  it  by  equidistanl  horizontal  piano. 

are  termed  horizontals  of  tJu  plane^  those  usually 

ken  the  references  of  which  are  entire  numbers. 

L0...If,  in  a  plane  given  by  its  horizontals,  a  line  be  drawn 

perpendicular  to  the  horizontals,  its  projection  <>n  the  plane  of 

■  will  be  also  perpendicular  to  the  projections  of  the 

horizontals.    The  angle  of  tin's  line  with  the  plane  of  reference 

ridently  the  same  as  that  of  the  given   plane  with   it,  and 

reater  than  the  angle  between  any  other  line  drawn  in  the 

plane  and  the  plane  of  reference.    This  line  is,  on  this  account, 

termed  tlo  litu   of  greatest  declivity  of  the  plane. 

1 1  —  1 1"  the  scale  of  declivity  of  the  line  of  greatest  declivity 
true  ted,  it  will  alone  Berve  to  fix  the  position  of  the 
plane  to  which  it  belongs,  and  to  determine  the  reference  of 
any  point  of  the  plane  of  which  the  projection  is  given.  For 
the  inclination  of  this  line-  and  that  of  the  plane  are  the 
same;  and  as  the  horizontals  are  perpendicular  to  the  line  of 
declivity,  the  point  where  the  horizontal  drawn 
through  the  given  projection  of  ;i  point  in  the  plain-  cuts  this 
line  will  determine  upon  the  scale  the  reference  <>t  the  hori- 

tal,  and,  therefore,  that  of  the  point. 
i  •_'... The  inclination,  or  declivity  of  a  plane   with   the   plane 

nco,  may  he  expressed  in  the  sarnie  way  as  the  inclina- 
tion of  its  line  of  greatest   declivity.    Tims:  </  />/<///<>  of  o?ie- 
y  <■/!   mi, ,  a  />/>'/,,    of  two-thirds^  ex- 
at  the  natural  tan-cut  of  the  angle  between  the  planes 


SYSTEM   OF    FORTIFICATION    DRAWING,  11 

and  the  plane  of  reference  are  respectively  represented  by  tlio 
fractions  J,  20-1  and  $. 

13. ..The  horizontal  distance  between  two  horizontals  of  a 
plane,  the  angle  of  which  is  given,  can  be  found  in  the  same 
way  as  the  horizontal  distance  between  two  points  of  a  line, 
the  inclination  of  which  is  given,  Art.  7,  by  dividing  the  dif- 
ference of  the  reference  of  the  horizontals  by  the  fraction  rep- 
resenting  the  inclination  of  the  plane;  in  like  manner  the 
difference  of  references  of  two  horizonals  will  be  obtained  by 
multiplying  their  horizontal  distance  by  the  same  fraction. 

14.. .To  distinguish  the  scale  of  declivity,  PI.  1,  Fig.  2,  from 
any  other  line  of  a  plane,  it  is  always  represented  by  two  fine 
parallel  lines,  drawn  near  each  other,  and  crossed  at  the  points 
of  division,  where,  the  references  are  written,  by  short  lines, 
which  are  portions  of  the  corresponding  horizontals. 

"With  the  foregoing  elements,  the  usual  problems  of  the  right 
line  and  plane  can  be  readily  solved. 


PROBLEMS    OF    THE    RIGHT    LINE    AND    PLANE. 

15...Piton.  1,  Pi..    1.  Fro.  8,     Having  the  projection*  <//<</ 
two  lines  thai  intersect,  to  find  the  angle  between 
//<>  in. 

Let  <i  h  be  the  projection  of  one  of  the  lines,  the  referen 
of  two  of  its  points  (10,80)   and   (4,90)  being  given  :   c  <h  the 
projection  of  the  other  line,  (10,30)  and  (5,0)  being  the  refer- 
ences "f  two  of  its  points;  (10,80)  being  the  point  of  intei 

tioll  of  the  tw<.  Lii 

Find  on  each  of  the  lines.  Art.  7.  a  point  having  the  same 
The  line  joining  these  two  point.-,  will   be 
horizontal,  and  projected  into  its  true  length;  taking  this  lino 
of  the  triangle  of  which  the  other  t  are 

respectively  the  true  lengths  of  the  portions  of  tl  iven 

lini  b  projected  betwet  □  I  L0,8  .  7.  the  angii 

the  vertex  will  be  tl •  [uired, 


IS  -MMI    OF     FOKTIFTOATIOM    OWAW1.N... 

]»;..'  Fro.  4.     Through  a  point ,  to  draw  a  Jlnepar- 

'tu . 
I  .  •  be  the  projection  of  the  poini ;  a  b  thai  of  the 

:'  which  the  two  points  (7,0)  and  (9,0)  are  known. 
il'Ii  o  draw  in--  '■ '/  parallel  t<>  a  b,  this  will  be  the  pro- 

-  .it  of  the  required  line:  and  as  its  declivity  is  t  ho  same 
that  <»r  the  given  line,  it  will  be  only  necessary  to  set  off 

from  c  toward  <L  the  same  distance  as  between  (7,0)  and  (9 
tain  a  point  (9,50)  as  tar  above  (7,60)   as  (9,0)   is  above 

1 7 . . .  1  * i : < . i . .  8,  Fig.  5.  Through  a  point  in  </  plane,  to  (hum 
u  i',n,  in  tin  j'/ii/o  with  (i  given  inclination. 

Lei  ocCbe  the  scale  of  declivity  of  the  given  plane,  and  a 
^iven  point;  and  suppose,  for  example,  that  the 
declivity  <-t'  the  plane  is  1-6,  and  that  the  declivity  of  the 
required  line  Is  L-10. 

1  >raw  the  horizontal  of  the  plane  (5,50)  which  passes  through 
the  point,  and  any  other  horizontal  as  (7,0).  The  projection  of 
the  required  line  will  pass  through  a,  and  the  portion  of  it  be- 
tween  the  two  horizontals  will  be  equal,  Art.  6,  to  the  differ- 
of  their  references,  or  i.5  feel  divided  by  the  fraction 
which  represents  the  inclination  of  the  required  line. 
Describing,  therefore,  from  a  an  arc,  with  this  distance  a  c,  or 
L5-T-1-10  L5  feet  as  a  radius,  and  joining  the  point  6,  where 
it  cuts  the  horizontal  (7,0),  with  a,  this  will  be  the  projection 
of  the  required  line. 

L8...Psob,  1.  IV.  L,  Fig.  6.  Having  tkret  points  of  a  planej 
istruct  its  horizontals  and  soaU  of  dscUtoity. 

Le1  a  (13,0),  I  (15,25)  and  <■  (15,50)  be  the  three  points. 
the  lowest  with  the  other  two,  and  construct  the  scales  of 
declivity  of  the  Lines  of  junction.  Art.  »;.  The  lines  joining 
the  same  references  on  these  two  lines  will  be  horizontals  of 
the  required  plane.  The  scale  of  its  declivity  will  be  found 
by  drawing  two  parallel  lines  perpendicular  to  the  horizontals, 
and  writing  the  references  pf  the  points  where  the  scale  inter- 

-  them. 


SYSTEM    OF   FORTIFICATION    DRAWING.  13 

19...Pkob.  5,  Pl.  1,  Fig.  7.  To  find  the  horizontals  of  a 
plant  pa8S(  d  through  a  <jiv<  n  Une  mid  parallel  to  a/mfh,  r  line. 

Let  a  5  and  o  d  be  the  projections  of  the  two  lines.  Prom 
a  point  (10,0)  on  c  d  draw  a  lino,  Prob.  2,  parallel  to  a  bj  and 
by  Prob.  4,  find  the  horizontals  of  the  plane  ol  this  line  and  <■ 
d  •  these  will  be  the  required  horizontals. 

20...Prob.  6,  Pl.  1,  Fig.  8.  To  find  fin  horizontals  of  a 
plane,  tJu  declivity  of  vjhieh  is  given,  and  which  passes  through 

a  g'i 'r>  n  Jim  . 

Lei  h  d  be  the  scale  of  declivity  of  the  given  line,  and  sup- 
pose,  fbr  example,  the  declivity  of  the  line  to  be  1-15  and  that 
of  the  required  plane  to  he  1-12. 

Since  the  horizontals  of  the  plane  must  pass  through  the 
points  of  the  line  having  the  like  references,  and  as  the  dis- 
tance in  projection  between  any  two  of  them,  Art  13,  will  he 
equal  to  the  difference  of  their  references  divided  by  the  frac- 
tion of  inclination  of  the  plane,  it  follows  that,  to  find  the  one 
drawn  through  I  (14,0),  for  example,  it  will  he  simply  m 
sary  to  describe  from  any  other  point,  as  a  (12,0),  an  arc  of  a 
circle,  with  a  radius  of  12  feet,  equal  to  the  quotient  just  men- 
tioned, and  to  draw  a  tangent  to  this  arc  from  1>.  If  any  other 
horizontal,  as  (16,0),  is  required,  which  would  not  intersect  the 
given  line  within  the  limits  of  the  drawing,  any  two  points,  a- 
(12,<M  and  { ]}. hi  f,,r  example,  may  he  taken  as  centres,  and 
two  arcs  he  described  from  them,  with  radii  of  12  :md  24  feet, 
calculated  as  above;  a  line  drawn  tangent  to  the  arcs  will  be 
the  required   horizontal. 

21 ... I'imc.  7.  Pl.  1.  Fig.  9.     TTa/oing  tJu  horizontals,  or  the 

of  declivity  of  two  :  to  find  tin  ir  inU  r*  et 

.h.in  the  points  where  any  two  horizontals,  as  (1#,0)  and 
< 1  l.o  .  in  one  plane  intersect  two  corresponding  horizontals  of 
the  other,  ami  the  line  bo  found  will  he  the  projection  of  tin1 
required  intersection. 

22.. .When  the  horizontals  are  parallel,  or  when  they  ar< 

nearly  parallel  that   their  points  of  intersection   cannol    be 

lily  found,  the  fo  method  may  he  taken:   I>raw 


II  •  i roM  db Lwnro. 

partlle]  \h  ■  ''.  PI.  1.  Fig.  LO.    These  may  be 

the  horizontals  of  an  arbitrary  plane  having  the 
and  (14,0),  as  the  two  corresponding 
hori  ich  of  the  given  plan 

of  the  horizontals  of  the  arbitrary  plane 
with  those  of  the  given  planes  will  determine  two  lines,  which, 
being  the  intersections  of  the  given  planes  with  the  arbitrary 
ill,  by  their  intersection  0,  determine  a  point  common 
to  the  three  planes,  and,  therefore,  a  point  of  the  intersection 
of  the  two  given  planes.  Assuming  any  other  two  parallels, 
a  b, «/'  ii.  as  the  horizontals  of  another  arbitrary  plane;  finding 
the  poinl  d  common  to  the  three  plain's,  and  joining  "  and 
<>'  by  a  line,  this  will  be  the  required  intersection. 

When  the  horizontals  of  the  two  planes  are  parallel,  one 
point,  a>  ",  will  be  sufficient  to  determine  the  intersection,  as 
projection  will  be  parallel  to  the  horizontals. 
23...Peob.  8,  Pl.  J,  Fig,  11.     To  find  when   a  gi/oen  lint 

8  -/  givi  a  plan* . 
Through  any  two  points  of  the  line,  having  the  same  refer- 
2,0)  ill.'1),  for  example,  as  two  horizontals  of  the  given 
plane,  draw  two  parallel  line-,  <i  A.  a'  //.  which  may  be  taken 
a.-  tin-  horizontals  of  an  abitrary  plane.  The  line  of  intersec- 
tion, i"  ".  oi'  this  plane  with  the  >/w  en  plane  being  determined, 
by  Prob.  7,  the  poinl  "  where  it  intersects  the  given  lino  will 
be  the  projection  of  the  required  point,  the  reference  of  which 
can  In-  found  from  the  scale  of  the  plane, 

•J  l...l'i;.  ,:.  '.'.    Pi  .    1,   FlG.    12.        '/'"    drOW  from    ilijn',1,    point 

,i  J*.  rj»  ndiexdar  to  <<  >/'<-,  a  plan* ,  itndfina  its  1,  ngtTu 

Lei  '/  il-.11!  be  tin-  given  point,  and  tin-  given  plane  be 

represented  1>\  it-  Bcale  of  declivity. 
'riic    projection   of  the   required    perpendicular  will    pass 

through  a  Bad   be  parallel  to  the  scale  of  declivity  of  the 
■  ii    plane.     The   angle   which    it    makes  with    the    plane   of 

the  complement  of  that  between  this  plane  and 

tlie  given   plane;   its  tangent,  therefore,  will  be  the  reciprocal 
of  the  tangenl  0/  that  of  the  given  plane. 


SYSTEM   OF    J'dUl  IM<  A'l  lo.\    IMtAWI.V..  15 

Drawing,  therefore,  through  a,  the  line  a  e  parallel  to  the 
scale  of  declivity  of  the  plane,  and  oonstructing  its  scale  of 
declivity,  Art.  7,  tins  will  be  the  projection  of  tjie  required  per- 
pendicular. The  point  0,  where  it  pierces  the  given  plane,  is 
found  by  Prob.  8,  and  its  true  Length  by  Art.  8. 

25...Curv<<l  and  Irr<  <jnhtr  Surfaces. 

All  other  surfaces  may,  like  the  plane,  Art.  7,  be  represented 
by  the  projections  on  the  plane  of  reference  of  the  curves  or 
lines,  cut  from  them  by  equidistant  horizontal  planes,  together 
with  the  references  of  these  curves;  as  many  of  these  curves 
being  drawn  as  may  be  requisite  to  determine  all  the  points  of 
the  surface  with  accuracy. 

In  the  more  simple  geometrical  surfaces,  a  single  horizontal 
curve,  with  the  projection  of  some  point  or  line  of  the  surface, 
will  alone  suffice.  For  example,  the  cone  may  be  represented 
by  the  projection  and  reference  of  any  curve  cut  from  it  by  a 
horizontal  plane,  with  the  projection  and  reference  of  its  ver- 
tex ;  a  cylinder  by  the  projection  and  reference  of  a  like  curve, 
with  the  projection  and  reference  of  one  of  its  right  line  ele- 
ments; a  sphere  by  the  projection  ami  reference  of  its  centre 
and  that  of  its   great  circle  parallel  to  the  plane  of  reference. 

26.. .This  method  of  projection  is  more  particularly  advanta- 
geous in  the  representation  of  irregular  surfaces,  which,  like 
the  natural  surfaces  of  ground,  for  example,  are  not  submitted 
to  any  geometrical  law,  and  in  solving  the  various  problems  of 
tangent  ami  secant  planes  to  surfaces  of  thy  character.  These 
surfaces  can  only  be  represented  by  the  projection  of  the  hori- 
zontal curves  cut  from  them  by  equidistant  horizontal  pla 
and  by  substituting  for  the  zone  of  the  real  surface,  contained 
between  any  two  horizontal  curves,  an  artificial  zone,  suh- 
jected  to  sonie  geometrical  law  of  generation  which  shall  give 
an  approximation  to  the  real  surface  sufficiently  accurate  for 

the  object  in  view.      Tie'  usual  method  of  doing  this  i.-  to  take 
two  consecutive  horizontal  cu  the  din  f  the  ar- 

tificial  surface  of  th<  B   right   line  SO    a-   to 

intersect   them,  and,   in  each  of  it-  1 


]«;  mi.'N    DRAWING. 

ieular  to  the  consecutive  tangents  to  one  of  the  our 
roper  curve  being  usually  taken  for  this  last  condition. 

If.  in   1'!.  1.  Fig.  L3,  for  exampl.  .  etc.,  arc  the 

r  the  horizontals  of  a  surface,  the  zone  between  the 
,-ur.  i  and  (7,0)  may  be  replaced  by  an  artificial  surface, 
tin-  position  of  tin-  generatrix  of  which,  at  any  point  of  the 
upper  curve  (7,0),  will  Ik-  determined  by  constructing  the  hori- 
•  il  tangent  at  that  point,  a.-  ./.  for  example,  and  drawing  << 
i.  perpendicular  t..  it.  and  intersecting  the  lower  curve.  The 
position  "t"  the  generatrix  •>'  b'  at  any  other  point  a' is  con- 

gtracted  in  like  manner. 

8T...T0  obtain  any  curve  of  the  artificial  /cue  intermediate 
to  the  two  directrices,  it  will  he  only  necessary  \<>  construct 
:..!i-  of  the  generatrix,  ami  to  find  on  these  the 
pointB  having  the  game  reference  as  the  required  curve.  The 
horizontal  of  the  surface  (6,50),  for  example,  will  bisect  the 
projections  of  the  generatrix  in  its  various  positions. 


I'KOHLKMS  OF   [RREGU1AR  SURFACES  AND  THE 
BIGHT  LINK  AM)  PLANE 

28...Pbob.  1".  I'i  .  1.  Fiq.  II.  Through  a  given  point,  in d 
vertical  plan*  which  intersects  a  surface,  to  draw  a  tang\  nt  (<> 
of  i/if,  rsi  ction  oftJu  plan<  and  surfaa . 
,50)  be  t^ie  given  point,  and  a  b  the  trace  of  the 
plane.  The  points  where  this  trace  intersects  the  horizontal 
curves  of  the  surface  will  be  the  projections  of  points  of  the 
carve. 

L' ;  any  arbitrary  line.  ;•-  ,/  ,-.  be  now  drawn  through  <i.  ami 
cale  of  declivity  he  constructed;  and   let  the  horizontal 
Lines  oe  drawn  between  the  points  having  the  same  references 
on  ./  c  and  a  b  where  the  tatter  cuts  the  horizontal   curved. 
Tin  intals  will  generally  make  differenl  angles  with  a 

id  the  o:  . ."  .  which  makes  the  smallest  angle  with 

it.  toward  the  descending  portion,  will  determine  on  the  curve 


SYSTEM    OF    KoKTIi  li  ATION     DKAWIM,.  17 

the  tangential  point.  To  show  tin's,  construct  the  scale  of  de- 
clivity of  the  line  thus  found,  of  which  a  (6,60)  is  the  projec- 
tion of  one  point,  and  (7,0),  on  a  &,  the  tangent  point,  another. 
This  is  most  readily  done,  by  drawing  through  the  points 
(10,o),  (O.oi,  etc.,  of  a  c.  lines  parallel  to  the  horizontal  (7."', 
and  finding  where  they  intersect  a  b,  in  which  the  required 
tangent  will  be  projected.  Ootnparing  now  the  references  of 
the  points  on  the  line  just  found,  and  assumed  as  the  required 
tangent,  with  the  references  of  the  points  of  the  curve  having 
the  same  projection,  it.  will  at  once  he  evident  that  these  two 
lines  have  only  the  point  projected  in  (7,0)  in  common,  and 
that  every  other  point  of  the  right  line  is  exterior  to  the  curve, 
and,  therefore,  this  line  must  be  tangent  to  the  curve  at  the 
point  determined  as  above. 

29m.Pb<  >b.  1 1,  1)l.  1 .  Fio.  1 5.     To  construct  tin  >  A  m<  tits  of  a 

with  a  given  vertex  which  .shall  envelop  a  given  surface. 

Let  (10,0),  etc.,  be  the  horizontals  of  the  given  surt'aee;  and 

.")  the  position  of  the  vertex  of  the  cone. 
From  </.  draw  a  b,  a  b\  etc.,  as  the  traces  of  vertical  planes 
which  pass  through  the  vertex  and  intersect  the  surface. 
Construct,  by  Prob.  1",  the  tangents,  from  a  to  the  curves  cut 
from  the  surface  by  the  planes  a  b,  etc.,  These  tangents  will 
be  the  required  elements. 

30...Pkob.  L2,  l'i..  1.  Fio.  L6.     To  find  the  curve  of inten 

oeloping  a  given  surfaa  by  a  horizontal  plane. 
Having  found,   by   J'roKs.   11    and    ll\  the  elements   of  the 
d  constructed  the  scale  of  declivity  of  each  one,  by 
joining  the  points  0,  d  a",  having  the  same  reference  as  the 
•  n  horizontal  phi:  \"i  for  example;  tin.-  will  form  a 

continuous  line  md'don,  which  will   be  the   projection  of  the 
points  win  re  these  elements  pierce  the  given  plane,  and,  th< 
the  projection  of  the  required  intersection. 
31...P&OB.  L8,   l'i.  2,  I  io.   1.     .1   limited  extent  oj 

ii< I  i/n  I  thin 

'ones  may  h  passed  through  thu 

all  th 

3 


18  SY8T1  V  Q  [<  All-'N     ni.ww  WO. 

.veil  point;  '  l".'  •  tc.j  the  hori- 

[veu  surface,  tin-  limits  of  which  are  the  Bector 

tained  within  the  arc  II  I>  (  .  and  the  two  radii  a  B  and  a 

• 
Taking  a -as  the  vertex  of  a  cone  which  shall  envelop  the 
.  -In-  elements  <»f  this  cone   can  he  fonnd  by 
:i  and  12.     Any  plane  that  can  be  passed  tangent  t<> 

this  Cone,  and  which  shall   not  intersect  the  surface  within  the 

•   limit-,  will  satisfy  the  conditions  of  the  problem. 
Prom  the  position  of  the  rertex  of  the  cone  with  respect  to 
tin-  surface,  it  will  be  Been  thai  a  horizontal  plane,  passed 

through  the  rertex,  will  cut  from  the  coin-  two  horizontals  a  b\ 

and  ■'  I-"  (8,0)  [the  firet  of  which  will  he  tangent  to  the  hori- 
zontal curve  (8,0)  of  the  surface,  and  the  second  a  h"  will 
pierce  the  Burface,  where  the  Limiting  arc  B  D  C  cuts  the 
6  horizontal  curve];  and  that  all  the  elements  projected 
within  the  angles  B  'i  V  and  Co  />'  will  lie  below  the  horizon- 
tal plane  (8,0).  Now.  if  the  elements  within  these  angles  be 
prolonged  beyond  the  vertex,  they  will  form  two  portions  of 
cones  having  the  same  elements  as  the  portions  below  the 
rertex;  and  it  is  evident  that  any  plane  passed  tangenl  to  the 

lower  portion,  as  V  -/   A',  within  one  of  these  angles;  will   leave 

this  portion  below  it.  and  0"'  corresponding  portion,  formed 
by  the  prolonged  elements,  above  it:  and.  in  order  that  this 
plane  -hall  satisfy  tin-  conditions  of  tin-  problem,  it  must  also 
Leave  the  portions  of  the  cone  wiflmn  the  angles  V .&  V\  and 
V*  a  O,  also  below  it.  The  same  reasoning  applies  to  planes 
passed  tangenl  to  the  portion.-  of  the  cone  within  each  of  the 
other  two  angles.     It  is.  therefore,  evident  that  a  plane,  which 

shall  satisfy  the  conditions  imposed,  must  leave  all  that  por- 
tion of  fhe  cone  which  lies  above  the  horizontal  plane  (8,0) 
through  the  vertex  below  it,  and  all  the  prolonged  portions 
corresponding  to  the  portions  belo\tf  the  plane  (8,0)  above  it. 
To  find  any  Buch  plane,  let  the  cone  be  intersected  by  a 

horizontal  plane,  a-  (9,0),  !>v  Prob.  L2.  This  plane  will  cut, 
from  the  portion  of  the  cone  within  the  angle  V  a  h",  a  curve 


SYSTEM    OF.   FORTIFICATION    DRAWIM..  19 

of  which  n  o  n'  is  the  projection;  the  two  extreme  points  of 
this  curve,  within  the  limits,  being  at  the  points  where  the 
horizontal  (9,0)  of  the  surface  elite  the  limiting  arc;  it  will  also 
cut,  from  each  of  the  prolonged  portions,  a  curve,  the  one  in  r, 
and  the  other  m  r' ;  the  extreme  point  m  of  ;//  /'  being  on  the 
prolongation  of  the  extreme  elements  C;  that  m'  of  the  other 
on  the  extreme  clement  a  B,  on  the  other  side,  prolonged. 
Having  obtained  these  three  curves,  let  tangent  lines  be  drawn 
from  the  points  m  and  m'  to  the  curve  n  o  W.  A  plane  passed 
through  either  of  these  tangents  and  through  the  correspond- 
ing element  of  the  cone  a  .?,  or  a  *',  drawn  through  the  tan- 
gential point,  will  he  a  tangent  plane  to  the  cone;  and  as 
either  of  these  planes  will  leave  the  curve  n  o  n!  on  one  side  of 
it.  and  the  two  curves  //>  r  and  ml  r'  on  the  other,  it  will  leave 
all  tlic  portion  Of  the  cone  corresponding  to  the  first  curve 
below  it, "and  the  portions  corresponding  to  the  other  curves 
ahove  it;  and  will,  therefore,  satisfy  the  required  conditions. 
The  same  will  hold  true  for  any  tangent  plane  to  the  cone 
along  any  element  drawn  between  the  points  s  and  «'/  since 
the  tangent  drawn  t<>  any  poinl  of  the  enrve  n  <>  n,  between 
the  |" lint.-  a  and  .*>',  will  leave  this  curve  on  one  side  of  it,  and 
the  other  two.  ///  /-  and  ml  r\  entirely  on  the  other. 

The  two  horizontal  elements,  a  V  and  a  b"  of  the  cone, 
will  be  parallel  to  the  asymptotes  of  the  curve  n  o  ■/  \ 
and  their  lines  of  prolongation  beyond  the  vertex  will  be  par- 
allel, in  like  manner,  to  the  asymptotes  of  the  two  curve.-,  m 
r  and  //''  / ■'. 

.Pros.  14.  Pl.  1.  l'i'..  L6.     Through  a  gvoe*  line,  topati 
a  flam  tc/ng<  ni  t 

1st.  Let  a  &  be  the  projection  of  the  given  line,  and  (10,0), 
(9,0),  etc.,  the  horizontals  <>t  the  surface.  From  the  point!  on 
the  line,  as  (10,0),  etc.,  draw  lines  tangent  to  the  horizontal 
curves  having  the  same  t  nt  which  rua 

with  the  projection  of  the  line  the  least  sngle  toward  the  den 
ding  portion  will,  with  the   line,  determine  the  requ 

pla: 


SYSTEM  Ol     I  "Ki!M(\\  i  [OM    DB  A\\  KNO. 

• 

For,  let   the  horizontal   tangent  (10,0)  be  the  one  which 

nukei  with  <t  5  the  least  angle  ;  from  the  other  points,  (9,0), 
etc.,  of  a  £,  draw  Line*  parallel  to  the  tangent  (10,0) ;  th 
lines  will  lie  in  the  plane  thai  contains  this   tangent  and  ab, 

and  will  be  horizontals  of  this  plane;  they  also  lie  respectively 
in  the  planes  of  the  horizontal  curves  (9,0),.  (8,0),  etc. ;  but, 
since  thej  fall  exterior  to  the  curves,  it  follows  that  their  plane 
lies  exterior  to  every  horizontal  curve  of  the  surface,  ex- 
cept at  the  curve  I  10,0)  when-  it  touches  the  surface  at  the 
point  of  contact  of  its  horizontal  (10,0)  with  this  curve. 

I'd.  When  the  line  a  5,  PI.  L,  Fig.  17,  is  horizontal,  let  tan- 
gents be  drawn  to  the  horizontal  curves  and  parallel  to  a  b. 
These  tangents  may  be  regarded  as  the  elements  of  a  cylinder 
which  envelops  the  surface,  the  tangent  plane  to  winch  will 
be  tangent  to  the  surface'.  To  find  the  element  of  contact  of 
the  plane  and  cylinder,  let  the  cylinder  and  given  line  be  in- 
d  by  an  arbitrary  vertical  plane,  of  which  o  d  is  the 
trace.  From  the  point  0,  where  the  line  pierces  this  plane,  let 
a  tangenl  line  be  drawn  to  the  curve  cut  from  the  cylinder  by 
the  plane,  by  Prob;  10.  The  point  of  contact  will  determine 
the  position  of  the  element  of  the  cylinder  along  which  the 
j. lane,  through  a  &,  will  be  tangent;  since  the  tangent  to  the 
curve  projected  in  0  <L  With  the  line  a  b,  will  determine  the 
tqpgent  plane  to  the  cylinder. 

:;d.  When  the  line  a  &,  PI.  1,  Fig.18,  is  so  nearly  horizontal 
that  tangents  cannot  be  drawn  from  its  points,  within  the  lim- 
it.-of  the  drawing,  to  the  horizontal  curves,  let  any  point  of 
the  line  as  0  (7,0),  he  taken  as  the  vertex  of  a  cone  enveloping 
the  surface;  a  plane  passed  through  the  line  and  tangent  to 
the  cone  will  be  tangenl  to  the  surface. 

Find,  by  Probs.  L0  and  11,  the  curve  m  r  n  cut  from  this 
cue  by  the  horizontal  plane  (8,0);  from  the  point  (8,0)  of  a 
I)  draw  a  tangenl  to  this  curve.  This  tangent,  with  the  line  a 
/>.  will  determine  the  required  plane, 

Peob.   \'k  I'i..    1,  Fi...  lit.     To  Jin  <7,  <i ]>]>rt ->ximately,  the 
,1  //•/><  r<  <t  <//'r,  a  right  Hue  pierces  a  surface. 


SVSTKM    OF    FORTIFICATION    DKAWINC.  21 

Let  (8,0),  (9,0),  etc.,  be  the  horizontals  of  the  surface,  and 
d  f  the  scale  of  declivity  of  the  line.  Through  any  two 
points,  as'a  (9,0)  and  c  (8,0),  draw  two  parallel  lines,  as  am 
and  c  n,  which  may  he  taken  as  the  horizontals  of  an  arbitrary 
plane  passed  through  the  given  line.  Joining  the  points  tn  n 
where  the  horizontals  of  the  arbitrary  plane  intersect  the  cor- 
responding horizontals  of  the  surface,  this  line  m  11  will  be  the 
approximate  intersection  of  the  plane  with  the  zone  of  the  sur- 
face between  the  horizontals  (8,0)  and  (9,0),  and  the  point  0, 
where  m  n  intersects  d  /,  will  be  the  approximate  point  re- 
quired. 

34:...Prob.  16,  Pl.  1,  Fig.  20.  To  find  tin-  intersection  of  a 
plant  and  surface. 

Let  (10,0),  (9,0),  etc.,  be  the  horizontal  curves  of  the  surface, 
ef  the  scale  of  declivity  of  the  plane. 

Draw  the  horizontals  of  the  plane  having  the  same  refer- 
ences as  the  horizontal  curves;  the  points  of  intersection  of 
these  lines,  in  their  respective  planes,  will  be  points  of  the 
required  intersection. 

When  it  is  desired  to  find  a  point  of  the  curve  of  intersec- 
tion intermediate  to  two  horizontal  curves,  if  the  reference  of 
the  required  point  is  fixed,  it  will  be  necessary  to  construct, 
Art.  27,  the  horizontal  curve  of  the  surface,  and  the  horizontal 
of  the  plane  having  this  reference;  their  intersection  will  give 
the  required  point.  If  the  reference  of  the  required  point  itf 
not  fixed,  draw  any  generatrix,  as  a  c,  of  the  zone  on  which 
the  required  point  ia  to  be  found,  and,  by  Prob.  8, Fig.  11, find 
the  point,  U  ".  where  '/  C  pierces  the  given  plane  ;  this  will  be 
th<-  required  point. 

... Application  "i    Pbecedhtg   Pboblemb.    The  following 
problems  will  aid  as  illustrations  of  the  preceding  subject  in 
its  application  to  the  determination  and  delineation  of  ] 
and  inrfai 

S...Pbob.  1,  Pl.  -.  Fio.  3.     2%  />/>/,<  .r},\ 

tin  anterior  Inn  and  seal*  of  declivity  of  its  ten  ino 

I  riruct  tin  ]>/<(/<<  of  tl 


M  II  1(    \TI<'N     UKAWLNl. 

'nclinati  g  //<-    rampart-el 

lead  <  the  plain  of  silt   to  the  terreplein. 

I  .  •  :  i.'  and  ft  76,0)  be  the  references  of  two  points  on 
tlir  exterior  line  of  the  terreplein,  and  m  n  its  scale  of  de- 
clivity :  let  the  rampart-elope  be  3-2;  the  declivity  of  the  ramp 
l  :-.  its  width  4.80  yards;  and  the  plane  of  site  bo  horizontal 
and  at  the  reference  (60,0). 

The  fool  of  the  rampart-slope  lying  in  the  plane  of  site 
will  be  horizontal,  and  will  be  determined,  Prob.  6,  Fig.  8,  by 
finding  the  line  of  the  slope  at  the  reference  (G0,0). 

Baving  the  two  bounding  linos  of  the  rampart-slope,  the  inner 
line,  o  '/.  "l"  the  ramp  is  constructed  by  assuming  a  point,  c,  on 
the  t"""t  of  the  rampart-slope,  as  the  point  of  departure,  and 
determining  the  line  of  l-:».  drawn  from  c,  on  the  rampart- 
slope,  by  Prob.  3,  Fig.  ■>.  Having  found  this  line,  which  is 
also  the  Line  of  greatest  declivity  of  the  ramp,  the  exterior 
line,  i  fy  of  the  ramp  is.  drawn  parallel  to  it,  and  at  a  distance 
4.80  yards,  equal  to  the  width  assumed  for  the  ramp.  The 
horizontals  of  the  ramp  will  be  perpendicular  to  these  two 
lines.  The  foot  of  the  ramp,  o  <\  will  be  a  horizontal  line 
drawn  through  the  point  of  departure*  The  top  of  it,  d  f\ 
will  be  determined)  by  Prob.  7.  Fig* '.'.  by  finding  the  intersec- 
tion of  the  ramp  and  the  terrepleinj  one  point  of  which  will  be 
the  point  <l  (76,80),  the  intersection  of  the  inner  line  of  the 
ramp  and  the  interior  line  of  the  terreplein. 

The  ramp  i>  terminated  on  the  exterior  by  passing  a  plane 
through  it.- exterior  line  <  /',  having  the  same  slope  as  the  ram- 
part-elope. This  plane  will  interseel  the  plane  of  site  in  a  line 
parallel  to  the  foot  of  the  rampart-slope,  and  the,  terreplein  in 
one  parallel  to  the  exterior  line  of  the  terreplein. 

87. ..Picon.  IS,  Pi..  2,  Fi<;.  .'i.     Having  given  the  lines  of  the 
■r  i  of  a  work,  and  the  scales  of  declivity  of  the  planes  of 
Uerior  crest  and  terreplein,  to  determint  the  lines  and sur- 
abarbetU  in  its  salient  for  jwp  guns. 

Let  a  b  be  the  scale  of  declivity  of  the  plane  of  the  interior 
it,  which,  as  the  terreplein  is  parallel   to  the  plane  of  the 


SYSTEM    OF    FoKTlI'iCATKiX    DKAWI.No.  23 

interior  crest  and  8  feet  below  it,  estimated  vertically,  will  also 
serve  as  the  scale  of  declivity  of  the  tcrreplein,  by  subtracting 
8  feet  from  the  references  of  the  former  to  obtain  the  corres- 
ponding references  of  the  latter.  Having  constructed  a  pan- 
coupe  of  4  yards  in  tbe  salient,  find  the  intersection  of  the  top 
surface  of  the  barbette,  which  is  horizontal  and  assumed  on 
the  drawing  at  the  reference  (82,75),  with  the  planes  of  the 
interior  slope,  this  intersection  will  determine  the  foot  of  the 
genouillere  of  the  barbette.  From  this  last  line  at  the  pan- 
coupe  set  back  along  the  capital  a  distance  of  8  yards,  and 
from  the  extremity  of  this  line  draw  a  perpendicular  to  the 
interior  crest  of  each  face.  The  pentagonal  figure  thus  marked 
out  will  be  the  space  for  the  gun  in  the  salient.  From  the 
foot  of  each  of  the  perpendiculars  set  off  along  the  faces  dis- 
tances of  12  yards,  for  the  lengths  along  the  interior  crests  to 
be  occupied  by  two  guns  on  each  side  of  the  salient.  Setting 
back  from  the  extremities  of  these  two  last  distances,  set  off 
perpendiculars  to  the  interior  crest  of  8  yards,  and  drawing 
lines  through  the  extremities  of  these  perpendicular  parallel 
to  the  interior  crests,  they,  with  the  two  perpendiculars,  will 
mark  out  the  exterior  bounding  lines  of  the  barbette.  By 
passing  planes  of  1-1  or  45°  through  these  exterior  lines,  and 
finding,  by  I 'rob.  7,  Fig.  9,  their  intersections  with  the  tcrre- 
plein, these  lines  will  be  tin'  t'oot  of  the  barbette-slopes.  A 
ramp,  having  a  slope  1-6,  Leads  from  the  terreplein  to  the  top 
of  tin-  barbette  ;  the  width  of  this  ramp  is  8.30  yard-,  its  inte- 
rior line  in  projection  being  on  the  prolongation  of  the  foot  of 
the  banquette-slope.    Tin1  ramp  is  terminated  by  aide-slopes  of 

1-1,  tin-    intersections   of  which    with    the    terreplein    ami    the 

slopes  of  the  barbette  and  banquette  are  found  by  Prob.  7, 
:*.     The  fool  of  the  rani].,  or  it>   intersection   with   tlie 

terreplein.  is  also  found    by  tie-  game  problem. 

A-  the  top  surface  of  the  barbette  is  horizontal,  it  may  !»«• 
necessary  in  some  cases  to  make  the  interior  crest,  along  the 

barbette,  also   horizontal,  in    which  case  the   superior   slope  of 


!  ..Kill  l<  All'i.N     DBAWINQ. 

along  the  barbette  being  higher  than  the  rest  of 

it.  the  t\v.»  pUnee  will  be  connected  by  a  plane  of  4-.*)°,  as  at  c. 

B8...Pbob.   L9,  I'i.  -.  1'i'i-  T     To  determine  //>•    hounding 

ip  leading  ttp  an  irregular  surface,  and  so 

ed  that  i  r  centrt  line  shall  nearly  ooincidi  with  the 

■    "face. 

Lei     8,     .    9,0),  BtC,  1"'  the  horizontal  curves  of  the  surface, 

ami  let  i  the  point  of  departure  or  foot  of  the  ramp. 

Assuming  the  declivity  of  the  ramp  !-'.»,  for  example,  from  a, 

with  a  radius  of  9  units,  describe  an  arc  and  join  by  a  right 

line  the  point  b   where   it   cuts   the   horizontal   (9,0)  with   the 

point     Repeat  this  construction,  from  b  to  c,  on  the  horizontal 

(  10,0);  and  BO  "H  to  the  top, ' .  or  point  of  arrival.     The  broken 

line  aJh&d-e  will  he  the  projection  of  the  axis.      But,  to  avoid 

the  angular  changes  of  direction,  tin'  .straight  portions  of  the 
1 1 1 : i \  he  connected  at  the  angular  points,  by  setting  off 
from  A,  for  example,  the  equal  distances  l>  a,  b  (f,  and  connect- 
ing these  points  by  an  are  of  a  circle  tangent  to  the  straight 
portions.  The  same  construction  being  repeated  at  the  other 
angular  points,  the  broken  hue  will  he  replaced  by  the  sinuous 
line  ,/  ,['  r\  etc.,  as  the  axis.  Saving  determined  the  axis,  the 
exterior  and  interior  lines  of  the  top  surface  are  drawn  par- 
allel to  the  axis,  and  at  a  distance  from  it  equally  to  half  the 
assumed  width  of  the  ramp.  From  the  position  of  the  axis, 
the  exterior  half  of  the  ramp  will  be  in  embankment,  and  the 
interior  in  excavation.  To  determine  the  side-slopes  of  the 
embankment,  pass  planes  through  the  Btraight  portions  of  the 
exterior  edge  of  the  ramp,  and  lind,  by  Prob.  6,  PI.  1,  Fig.  8, 
the  horizontals  of  these  planes,  and,  by  Prob.  1G,  Fig.  20,  the 
intersections  of  these  planes  with  the  irregular  surface.  The 
plane  Burfaces  of  the  Bide-slopes  thus  determined,  are  con- 
nect.■■!  by  curved  surfaces  whic-h  pass  through  the  curved  lines 
of  the  exterior  edge.  These  surfaces  may  be  determined  as 
follows  :  Take,  for  example,  the  point  n  at  the  foot  of  the 
plane  side-slope  J,  where  it  cuts  the  radius  prolonged,  of  the 
arc  a!  d  ;  and  the  point  0  on  the  radius  through  d  where  it 


BYBTBM  of  fortification  du.wvim,.  25 

cuts  the  foot,  of  the  plane  side-slope  B.  The  lines,  of  which 
n  v  and  o  u  are  the  projections;  will  evidently  have  the  same 
inclination,  and  they  may  be  assumed  as  the  lines  of  junction 
of  the  plane-slopes  A  and  B  and  the  curved  side-slope  xs. 
This  curved  sidenslope  may  then  he  generated  by  the-motion 
of  a  right  line,  which  has  the  top  line  of  which  v  u  is  the  pro* 
jectiou  for  its  directrix,  whilst  in  its  motion  it  makes  a  con- 
stant angle  with  the  plane  of  comparison,  ami  its  projections 
are  constantly  normal  to  the  arc  v  u.  From  the  construction 
comprising  these  conditions,  the  foot  n  o,  of  the  curved  portion 
x,  of  the  side-slope  is  determined.  The  same  constructions  are 
repeated  to  obtain  the  portions,  C,  of  the  plane,  and  y  z  of  the 
curved  side-slopes,  with  the  line  m-?i-o-j)-q-r-s  the  foot  of  these 
slopes. 

The  side-slopes  of  the  part  in  excavation  A\  B\  C  and 
«f  y  with  the  line  m' -ri -o' -p' -(/ -r' ,  are  determined  by  like  con- 
structions. 

The  portions  of  the  top  surfaces  of  the  ramps,  bounded  by 
the  arcs  of  circles,  are  helicoidal  surfaces,  of  which  the  axis  is 
the  directrix  and  the  plane  of  comparison  the  plane  director. 

The  curved  surface  side-slopes  are  also  evidently  helicoidal 
surfaces,  the  directrices  of  which  are  the  curved  lines  above 
mentioned;  and  the  vertical  lines  through  the  centres  of  the 
arcs  the  projections  of  these  lines. 

Remabkb.     In  the  Figure,  the  declivity  of  the  side-slopes  of 
the  embankment  is  one-half  the  excavation.    The  declivities 
of  the  curved  portions  of  the  top  are  greater  than  thoa 
plane  surfaces,  the  difference  depending  on  the  angle  between 
the  straight  portions  of  the  a] 

S9.../'/"/i,  Section,  Elevation  and  Profile. 

In  delineating   permanent  fortifications,  horizontal  projec- 
tions and  horizontal  sections,  both  of  which  go  under  the  gen- 
era] name  wplans,  are  used  to  represent  the  relative  positions 
of  the  parts  and  their  dimensions  horizontally,     tntei 
of  the  part-  by  vertical  planes  D  any  required  direction, 

and   termed  .    .-di^v  the   relative    j  and    dinien- 

4 


.  ,  !i  1.     Vll-'N      l»i:  A  WIN... 

all  the  parts  in  the  plane  of  section,  both  horizontally 
jections  on  :i  vertical  plane,  termed  sleva- 
nt  tin-  forms  of  the  exterior  surfaces 
projected  and  their  relative  positions  vertically. 
/'    •     •   an       ctions  made  by  vertical  planes  passed  perpen- 
dicular i"  the  horizontal  projections  of  the  interior  crests  of 
the  parts  where  the  profiles  are  taken;  they  give  the  vertical 
and  horizontal  distances  between  the  points  in  tli<'  plane  <>t'  the 
profile.     Usually,  s  profile  only  shows  the  bounding  lines  of 
the  parts  intersected,  thus  presenting  nothing  more  than  an 
outline  of  the  parts. 

In  giving  a  horizontal  section,  it  is  customary  not  only  tp 
delineate  the  forms  Contained  in  the  plane  of  section,  but  to 
project  upon  this  plane  all  the  parts  which  are  Been  below  it, 
ami  in  some  cases  parts  which  are  covered  by  others,  tin-  (Jut- 
lines  of  tin-  latter  being  shown  by  broken,  or  dotted,  lines,  to 
distinguish   them  front  the  outlines  nt'  tin-  parts  in  view,  for 
which  full  lines  are  used.     A  like  method  i-  sometimes  em- 
ployed in  sections,  the  visible  parts  beyond  the  plane  of 
tit. n  being  projected  upon  it ;  thus  combining  an  elevation  ami 
in  in  the  Mime  figure. 
For  the  perfect  comprehension  of  a  fortification,  not  only 
will  all  of  the  foregoing  modes  of  delineation  be  requisite,  hut 
the  references  of  all  the  points  and   lines,  as  well   as  the  verti- 
cal and  horizontal  distances  that  determine,  the  relative  posir 
of  the  points,  must  he  carefully  written  on  each  figure. 
In    PI.   :;.  Figs.    1.  2,  ::.  which   show  the   plan,   section   and 
elevation   of  tin-  end  of  the  face  of  a  work,  an   illustration  i$ 
given  of  the  usual  manner  in  which  such   drawings  are   made; 

and  the  same  system  will  he  pursued  in  the  figures  which  fol- 
low 1! 

\fi... Observations  <<n  tin  iMa/M  for  obtaining  accuracy  in 
drawings. 

The  first  requisite  in  all  drawings   intended  to  represent   not 

only  tin-  outline  of  the  forms  of  objects,  hut  to  afford  the 
mean-  of  determining  the  exact  dimensions  of  each  part,  is 


3V8TEM   OF   FORTIFICATION    DBAWINO.  27 

minuU  accura<nf,  both  in  the  geometrical  constructions,  and  in 
writing  down  all  tetters  and  numbers  which  serve  either  as 
references  or  to  give  the  dimensions, 

To  attain  this  end,  so  tar  88  regards  the  geometrical  part, 
judgment  is  to  be  exercised  in  the  selection  of  the  means  for 
establishing  on  the  drawing  the  positions  of  the  various  points 
which  are  either  given  or  to  be  found;  as  one  method, 
although  in  theory  as  correct  as  some  other,  may  not,  in  prac- 
tice, be  found  to  yield  as  satisfactory  results.  Attention  to 
the  following  remarks  will  serve  both  to  illustrate  the  mean- 
ing here  intended,  and  to  give  some  simple  practical  methods! 

1st.  In  setting  off  several  distances  along  a  line,  whether 
equal  or  unequal,  the  most  accurate  method  is  to  commence  by 
first  setting  off  the  entire  distance,  and  then  the  several  parts; 
taking  care  to  verify,  from  the  scale,  the  aggregate  of  the 
ral  partial  distances;  thus,  in  the  annexed  PI.  2,  Pig,  5, 
where  the  aggregate  of  all  the  partial  distances  is  60.83  feet, 
commence  by  setting  off  the  entire  distance  ''»'»'.  33  feet;  next 
tH f.33,  which  is  the  sum  of  the  two  distances,  20'  and  c5<»'.33, 
then  verify  the  remaining  K»'  by  the  scale. 

2d.  When  a  distance  to  be  set  off  18  so  small  that  it  cannot 
be  laid  down  with  accuracy  by  the  points  of  the  dividers,  the 
>wing  method  may  be  employed:  sit  back,  from  the  point 
from  which  the  required  distance  is  to  be  set  off, any  arbitrary 
distance,  then  Bet  forward,  from  this  last  point,  a  distance 
equal  to  the  sum  of  this  arbitrary  distance  and  the  one  re- 
quired; thus,  in  PI.  2,  Pig.  6,  where  2'  is  to  be  set  off  from  a 
toward  < .  -<  I  back  from  <>  say  30'  to  A.  then  from  h  88*  I 

8d.  In  setting  off  a  point  at  a  given  perpendicular  distal 
from  a  line,  instead  of  drawing  a  perpendicular,  in  the  first 
place,  to  tlic   line,  it    will   mostly  be  found    more   speedy,  and 
more  accurate,  to  take  off  from  the  scale  the  given  distance,  in 
the  dividers,  and.  Betting  one  point  on  the  paper,  bring  the 

r  so  that  the  ar<-  •  ..  scribed  by  it.  with   the  g\\ 
as  a  radius,  shall  be  tangent  to  the  line ;  thus,  in  i'  ..7. 

wishing  ffc  at   20*  from  >>  /',  take  2C  in  the  divider.-. 


OF    FOKTIFH    \'I  KMJ    DRAWING. 

.  find  where  one  point  must  be  placed  bo  that 

the  other  d(  an  arc  will  touch  a  h.    This  method  will 

d  convenient  in  drawing  a  parallel  to  a  line  at  a  given 

diatance  from  it  by  Betting  off  another  point  in  the  same  way. 

4th.  In  Betting  off  several  points,  for  the  purpose  of  drawing 

•  ral  parallels  to  a  given  line,  as,  for  example,  the  lines 

which  bound  the  planes  of  a  parapet,  it  will   be  found  most 

-  dy  and  accurate  to  draw  upon  a  Blip  of  smooth  thin  paper 

two  lines  perpendicular  to  each  other;  mark  on  one  of  the 

lines  the  reaped  □  distances  from  the  other;  then  cut 

tin-  paper  close  to  the  line  along  which  the  given  points  are 

marked  off;  so  that,  when  the  strip  is  laid  upon  the  drawing, 

the  other  line  marked  upon  it  being  Laid  upon  the  line  of  the 

draa  ing  to  which  the  parallels  are  to  be  drawn  can  be  pricked 

«.H".  either  by  a  sharp-pointed  pencil,  or  in  any  other  way.     In 

PL  -.  1  "'Lr.  s.  a  b  i>  the  line  of  drawing;  .1  the  Btrip  of  paper, 

.  etc,  the  distances  at  which  the  parallels  are  to  be 

drawn  from  a  //,  marked  oil' on  the  edge  of  A  perpendicular  to 

the  line  /',  which  line,  when  .1  is  laid  on  the  drawing,  should 
coincide  with  </  />.  If  the  line  ,/  l>  is  sotnewhal  long,  it  will  he 
heti<  r  to  -et  off  these  |<oiut>  near  each  of  its  extremities  than 
to  draw  the  parallels  by  aid  of  the  ruler  ami  triangle. 

5th.    When  a  point  18  to  he  constructed   by  means  of  the  in- 

ten  i    two   Lines  arbitrarily  chosen,  such   a   position 

should  he  assumed  tor  the  arbitrary  lines  that  they  .-hall  not 
form  a  \<v\  acute  angle,  as  iu  that  case  their  point  of  intersec- 
tion mighl  not  he  determined  by  the  eye  with  accuracy.  For 
tnple,  in  erecting  a  perpendicular  to  a  line  at  a  given  point, 
ami  in  Like  problems,  in  which  points  are  found  by  the  inter- 
sections  of  arcs  of  circles,  it  will   he  usually  mosl  convenient, 

and  best,  to  take  for  the  radii  of  the  arcs  the  distance  between 

their  centres,  a.-  the  angle  between  the  tangents  to  the  arcs  at 
their  point  of  intersection  will  then  he  60°,  which  is  sufficient 
to  give  accurately  the  point  where  the  lines  cross.     In  <■; 
like  I  :_--.  l".  11.  A.rts.  22,  23,  the  arbitrary  lineB  a  l>,  a  b\  etc, 
should   he  so  chosen   a-  to   intersect    the  horizontals  nearly  at 


SYSTEM   OF   FORTIFICATION    I'KAWlNo.  v29 

.  right  angles,  and  so,  also,  that  the  resulting  lines,  by  which  the 
points  ".  "'  are  determined,  shall  not  intersect  in  too  acute  an 
angle. 

In  all  Buch  cases  of  determining  points,  and  even  where  *a 
point  is  peeked  into  the  paper  by  a  sharp  point,  it  will  be 
found  well  to  mark  the  point  thus  _.  by  a  small  circle  drawn 
around  it  with  the  lead  pencil,  as  this  will  present  the  point 
with  more  distinctm 

6th.  In  determining  a  portion  of  a  line,  by  the  construction 
or  two  arbitrary  points,  the  points  should  be  so  chosen  that 
the  portion  required  may  fall  between  them  and  not  beyond 
them.  In  PI.  1.  Fig  10,  for  example,  it'  the  required  portion 
of  the  line  of  intersection  of  the  planes  extended  on  either 
side,  beyond  0,  or «/,  or  beyond  both,  the  lines  </  A,  <■<!.  etc. 
should  be  so  chosen  as  to  bring  0  and  <>'  as  far  apart,  at  least,  as 
the  length  of  the  required  portion  of  the  line  which  they  serve 
to  determine. 

7th.  No  m€ans  of  verifying  the  accuracy  of  the  construc- 
tion of  points,  or  lines,  should  be  omitted.  In  PI.  1,  Fig.  9 
for  example,  other  corresponding  horizontals  should  he  drawn, 

and  if  the  line  of  intersection  determined  by  the  two  points 
first  found  is  correct,  their  points  of  intersection   also  will  fall 

Upon    it.        In    PI,  1,  Fiir>.  !'.  1".  the    Scale    of  declivity    of  the 

line  ..f  intersection  being  determined,  the  references  of  the 
points,  where  it  intersects  the  scales  of  declivity  of  the  planes, 
should  l.e  the  same  as  the  same  points  on  tic  if  the  line 

been  accurately  determined.     A  general  and  minute  ven- 
ation "f  all  tin  parts  of  the  drawing  should  he  made  before 
any  portion  ..f  it  i-  put  in  ink.        % 
Mli.  a  no*   unimportant  element  in  the  attain- 

t  of  accuracy  in  drawing.     A  few  minutias,  when  attended 
to,  will  Bubeerve  this  end. 

That  part  of  the  paper  on  which  the  draughtsman  is  not 
workii  _-.  Bnould  he  kept  covered  with  (dean  pap 

the  •  the  board  1  fold  over  the  draw 

which  B  liould  he  similarly  pp 


\ll«'N    DRAWING* 

Before  oommencing  the  daily  work,  the  paper  should  be 
fully  duited,  and  the  and  triangles  be  carefully 

-1  with  a/dean  dry  ra 

few  lin.  -  rtruction  as  possiblejshould  be  drawn  in 

il ;  and  only  thai  part  of  each  which  may  be  strictly  nee 

nine  the  point  sought  A-.  for  example,  whew  a 
to  !"•  found  by  the  intersection  of  two  arcs  of  circl 
when  tin.'  position  of  the  point  can  be  approximately  judged  of 
by  the  eya.  only  a  portion  of  one  arc,  which  will  embrace  the 
t,  may  be  drawn,  ami  the  point  where  the  Becond  arc  would 
intersect  the  first  be  marked  without  describing  tin-  arc  In 
PL  1.  Fig.  10,  instead  of  drawing  the  entire  lines,  a  J,  c  <L  etc^ 
it  would  De  simply  necessary  to  mark  the  points  only  where 
they  cut  the  horizontals,  and.  in  like  manner,  tlm  points  <>  and 
ft  might  be  marked  without  drawing  the  entire  lines. 

No  more  of  any  line  of  the  drawing  should  be  made  in  pen- 
cil than  what  is  to  remain  permanently  in  ink. 

0th.  In  inking  the  lines,  the  following  directions  will  be 
found  useful : 

Efface  carefully  all  pencil  lines  that  are  not  to  be  inked,  and 
those  parts  of  the  permanent  lines  which  are  not  to  remain, 
before  commencing  t<>  ink. 
When  right  lines  arc  tangent  to  curves,  put  in  ink  the  curve 
e  the  right  line;  draw  all  arcs,  of  equal  radii  at  once, one 
after  the  other;  If  several  arcs  an-  to  Ik-  described  from  the 
same  centre,  it  will  he  well  to  put  ;i  tain  hit  of  quill  over  the 
point  tor  the  end  of  the  dividers  to  rest  on,  to  avoid  making  a 
hole  in  the  drawing. 
It'  the  drawing  is  not  to  l^e  polored  with  the  brush,  all  the 
lines  of  one  color  should  he  put  in  before  co'mmencing  on  th< 
of  another. 

If  one  of  tin-  bounding  lines  of  a  surface  is  to  ho  made 
heavier  than  the  others,  its  breadth  should  ho  taken  from  the 
surface  they  limit  and  not  he  added  to  it;  and  when  the 
heavy  line  forms  the  boundary  of  two  surfaces,  its  breadth 
must  he  taken  from  the  one  of  greatest  declivity. 


sV.-'ll.M    01     l COB  I  IFKATI0N    DRAWING.  31 

10th.  When  the  drawing  is  to  be  colored,  all  lines  that  are 
not  to  be  black  may  be  pul  in  firsl  with  black— making  them 
very  faint,  so  that  they  may  receive  theii  appropriate  colors 
after  the,  drawing  is  otherwise  completed. 

No  heavy  line  should  be  put  in  until  the  work  with  the 
brash  is  completed. 

When  all  the  lines  are  in,  the  drawing  should  be  thoroughly 
cleaned  with  stale  bread-crumb;  and  then  have  several  pit- 
chers of  water  dashed  over  it,  the  board  being  placed  in  an 
inclined  position  to  allow  the  water,  colored  by  the  ink  lines, 
to  escape  rapidly,  and  not  to  discolor  the  paper. 

11th.  In  aging  the  brush,  whether  for  flat  tints,  or  graded, 
the  requisite  depth  of  tint  should  be  reached  by  a  number  of 
faint  tints  laid  over  each  other;  this  is  especially  necessary  in 
laying  tints  of  blacks,  browns  and  reds. 

To  obtain  an  even  flat,  or  graded  tint,  on  dry  paper,  is  very 
difficult  for  a  beginner.  The  best  plan  for  this  is,  first  to  wet 
with  a  large  brush,  or  clean  rag,  the  surface  on  which  the  tint 
is  to  be  laid,  then,  with  a  slightly  moist  rag,  clear  the  surface 
of  water,  and  before  the  paper  has  time  to  dry  lay  on  the  tint. 
With  this  precaution,  the  heaviest  tints  of  Chinese  ink,  the 
most  difficult  of  all  to  manage  OH  dry  paper,  can  be  neatly  laid 
down. 

12th.  The  lettering  and  numbering  of  a  drawing  should  be 
in  ordinary  printed:  character;  this  is  particularly  requisite  in 
the  numbering,  to  avoid  misapprehensions  which  might  arise 
from  individual  pecularities  in  writing  numb 

As  has  been  already  remarked,  references  are  written  in 

black,  within  brackets,  which,  when    practicable,  embrace  the 
.t  referred  to.     When  not  practicable,  a  small  dotted  line 
may  lead  from  the  point  to  the  n  »,50); 

but  to  distinguish  r<  P  from  other  numbers  the  designa- 

tion of  the  unit  is  omitted. 

All  horizontal  distances  between  point-   .are   written   upon   a 

dotted  line  drawn  betwi  en  the  point-,  with  an  arrow  head  at 

partial   di.-tanc  a  in  a  right   lin< 


SYSTEM  01     1  "Kill  1<  AXIOM    DB  \w  IXC 

marked,   it   will   lie   abo  well  to  mark   the   total  distance — the 
latter  may  be  written  above  or  beneath  tin-  former,  El.  9. 

In  writing  horizontal  distances,  the  usual  designation  of  the 
unit  i.-  always  written  thus;  y  for  yards, '  for  feet,  etc.  All 
the  numbers  musl  be  expressed  in  tin-  same  unit;  the  frac- 
tional parts  being  in  decimals. 

References  and   horizontal  distances  cannot  he  too  much 

multiplied,  in  order  t"  avoid  misapprehensions,  and  the  results 

rrora  of  construction,  is  well  a-  to  save  ^ie   time  that 

would  he  taken  in  applying  dividers  to  the  drawing  to  find, 

from  the  scale  affixed  to  it.  the  dimensions  of  any  part. 

A  scale  very  accurately  constructed  should  he  affixed  to  the 
drawing  before  it  is  cut  from  the  hoard  ;  so  that  the  shrinkage 
of  the  paper,  which  is  about  L-500,  may  affect  all  the  parts 
equally,  and  the  scale  thus  In-  made  to  correspond  to  the  real 
lengths  of  the  lines  on  the  drawing.  The  scale  should  he  di- 
vided according  to  the  decimal  BVBtem,  as  being  most  con- 
venient for  counting  off. 

The  lir.it  division  of  the  scale  should  furnish  the  units,  and 
also  their  decimal  parts,  if  the  scale  hears  that  proportion  to 
the  true  dimension,-  of  the  object  represented  which  will  ad- 
mit of  these  divisions.  This  first  division  is  numbered  from 
right  to  left,  PI.  L\  Fig.  !»,  the  zero  point  being  on  the  right, 
the  10  point  on  the  left  ;  the  succeeding  divisions,  to  50  inclii- 
ould  each  he  equal  to  the  first  division,  containing  ten 
uint.-  each.  The  remaining  divisions  may  contain  fifty  units 
each.  It  Mill  he  >eeii  that  any  number  of  tens,  units,  or  frac- 
tional part.-  of  a  unit,  can  thus  he  readily  taken  off  from  the 
scale  by  the  dwiders.  The  scale  should  he  long  enough  to 
'he  dimensions  of  the  longest  line  on  the  drawing. 

The  proportion  which  the  scale  hears  to  the  true  dimensions 
of  the  object  should  he  written  above  the  scale ;  thus,  seals  one 
'in.},  /.-  t.  n  yards,  <>,■  L-360.  And  the  designation  of  the  unit 
of  the  drawing  should  he  annexed  to   the    last   division  on  the 

.  S,  a.-  yds.  for  jBldatJ't,  for  feet,  etc. 


PERMANENT    FORTIFICATION. 


PRELIMINARY  CONSIDERATIONS. 


41. ..The  term  j»  rmam nt  fortification  is  applied  to  those  de- 
fences which,  constructed  of  materials  of  a  durable  nature,  and 
designed  for  permanent  occupancy  by  troops,  receive  such  a 
decree  of  strength  that  an  enemy  will  be  forced  to  the  opera- 
tions either  of  a  siege  or  a  blockade  to  gain  possession  of  them. 

42. ..The  object  of  such  defences  is  to  secure  the  permanent 
military  possession  of  those  points,  either  on  the  frontiers  or  in 
the  interior  of  a  State,  which  must,  at  all  times,  have  a  well- 
defined  bearing  on  the  operations  of  a  defensive  or  an  offen- 
sive war. 

r:...l'<>r  the  attainment  of  this  object,  the  following  general 
condition.-  should  be  fulfilled  in  the  arrangement  of  such  de- 
fence;-: Let,  they  should  be  of  sufficient  strength  to  resist  with 
.-access  all  the  ordinary  means  resorted  to  by  an  assailant  in 
an  open  assault;  2d,  be  provided  with  suitable  shelters  to  pro- 
tect thy  troops,  the  armament, and  the magaQnea  of  provisions 

Bad   munitions  of  war   required  for  their  den  :n-t    the 

active  measures  of  the  assailant,  of  e-. .  :  ::d. 

be  so  planned  that  every  point  exterior  to  the  thin 

cannon   range   .-hall    be    thoroughly   swept   by  their  fire;  4th, 

have  secure  and  easy  m<  .  ominunication  for  the  move- 

6 


:m  \ni:nt   works. 

incuts  of  the  troops,  both  within  the  defences  ami  to  the  e\- 
5th,  and  finally,  be  provided  with  all  such  accessory 

naive  in.  the  natural  features  of  the  position  itself 

may  afford,  to  enable  the  garrison  to  dispute  with  energy  the 
occupancy    by  the  assailant,  of  every   point  both  within  and 

rior  t(»  the  defenc 
Tin'  defensive  branch  of  the  military  engineer's  art  consists 
in  a  knowledge  «>t  the  means  which  are  employed  to  fulfil  the 
above  conditions,  and  of  their  suitable  adaptation  to  the 
natural  features  of  the  positions  ho  may  be  called  upon  to 
fortify. 


IWHXEXT  ELEMEXTS  OF  PER1IAXEXT  WORKS, 


(iKNKRAL  PROFILE. 

•I  I. ..The  first  condition  laid  down  for  permanent  defences, 
security  from  open  assault,  supposes  a  Btrength  of  profile 
greatly  superior  to  that  which  is  given  to  temporary  works. 

l.'....'1'lic  usual  and  most  simple  form  of  profile  for  perma* 
iM-nt  works  consist  of  a  rampwrt^  a  parapet,  and  a  ditch,  the 
ioarp  and  oounterscarp  of  which  are  faced  with  steep  malls  of 
ttone,  or  brick)  and  exterior  to  which  a  glacis  is  usually  thrown 
up.  When  the  ditch  contains  at  all  times  a  depth  of  water 
sufficient  to  prevent  it>  being  forded,  the  scarp  and  counter* 
scarp  may  be  simply  Blopes  of  earth  like  those  of  field  works; 
the  water,  with  ordinary  vigilance  on  the  part  of  the  de- 


COMPONENT    ELEMENTS  OF    PERMANENT   WORKS.  35 

fence,  will  give  security  from  surprise,  and  all  the  other  ordi- 
nary means  of  an  open  assault. 

46. ..The  rampart,  A,  PI.  3,  Figs.  4,  6,  is  an  earthen  mound, 
raised  above  the  natural  level  of  the  ground,  ami  upon  which 
the  parapet,  B,  is  placed.  The  rampart  thus  serves  to  give 
the  troope  and  armament,  which  are  placed  on  top  of  it  and 
behind  the  parapet,  a  commanding  view  over  the  ground  to 
lif  guarded  by  the  lire  of  the  defences;  whilst,  at  the  same 
time,  it  increases  the  obstacle  to  an  open  assault,  by  the  addi- 
tional height  it  gives  to  the  scarp. 

47.. .The  top  surface  of  the  rampart,  h  c,  in  rear  of  the  para- 
pefc,  termed  the  terreplein,  affords  the  troops  and  armament  a 
convenient  position  for  circulation  from  point  to  point,  where 
they  are  sheltered  from  the  direct  views  of  the  assailant's  fire. 

4s. ..The  rampart  is  usually  terminated  on  the  interior,  a  b. 
by  allowing  the  earth  to  assume  either  its  natural  slope  or  one 
somewhat  less  steep,  and  which  is  termed  the  rampartrtlope. 
In  cases  where  this  slope  would  take  up  too  much  of  die  ground 
within  the  defences  it  is  replaced  by*  wall, termed  theixwadt 
wall)  which  rises  from  the  level  of  the  interior  ground,  termed 
the  parad* .  to  the  interior  line  of  the  A  rrepli  >n. 

id.. .Inclined  planes  of  earth,  termed  ra/nj/s,  lead  from  the 
parade  to  the  terreplein,  being  placed  against  the  rampart-slope 
or  the  parade  walL  The  ramp.-  arc.  in  some  cases,  terminated, 
inwardly,  with  the  same  slope  as  that  of  the  rampart  ;  in   oth- 

.  this  slope  is  replaced  by  a  wall,  which  rises  to  she  top  ,-ur- 
of  the  ram]-,  or  a  little  above  it. 

.'."...Tin'  parapet,  serving  the  same  pm  permanent 

D  field  works,  receive  ne  general  form  as  in  the  lat- 

ter,    [nsome  cases,  the  exterior  slope,  PL  •'•.  V  j.  12, 
placed  by  a  wall,  which,  resting  on  the  top  of  the  scarp  wall, 

level  of  the  snpi  rior  .-lope.     The  exterior  sloi 
the  parapet  usually  rises  from  the  top  of  the  scarp  wall,  leai 
I  narrow  berm  betwi  i  □  it  and  the  scarp  or  the  wall. 

thrown  so  far  to  the  n  ar  of  I  I ' 

8,  1   _-   9,  10,  ai  >m  for  a  communication, 


OOMl'oNl  M     1  !.l  M  HUMAN!  NT    Works. 

i  front  of  tin-  parapet,  in  which  tlic  troops  can  circulate 
undi  r  from   lire  being  masked  either  by  an   earthen 

parapet,  or  by  a  wall.  I >.  Tliis  covered  communication,  G7,  is 
termed  an  exterior  corridor,  or  cJiertyvrirde-rondee. 

51...The  scarp  wall,  C,  PI.  3,  Figs.  4,  6,  retains  the  earth  of 
tin-  rampart  and  parapet,  and  forme,  by  its  height  ami  steep* 
.  tli.'  chid'  obstacle  to  an  open  assault*  The  top  stone  of 
the  wall.  l\  termed  tin-  cotdon,  or  coping,  projects  beyond  its 
face,  and,  serving  as  a  la/rmeir,  or  drip,  protects  it  from  the 
effects  of  the  rain-water  which  rims  from  the  parapet  upon  the 
coping. 

52.. .The  line  in  which  the  face  of  the  scarp  wall,  prolonged, 
would  intersect  the  coping,  is  termed  the  magistral.  This  is  a 
very  important  line  in  drawing  the  plans  of  permanent  works, 
serving  as  the  directing  line  to  fix  (both  upon  the  drawing  ami 
upon  tlu'  ground  in  setting  out  the  work). the  dimensions  and 
relative  positions  of  all  the  bounding  lines  of  the  parapet  and 
other  parts. 

53. ..Th<-  counterscarp  wall,  er,  renders  the  ditch  of  more 
difficult  access  from  without  than  an  earthen  slope  would:  and 
when  of  sufficient  height  and  steepness,  it  tonus  a  very  serious 
obstacle  to  an  open  assault.  It  receives  the  same  general  forms 
as  the  scarp  wall. 

..I. ..The  glacis,  F,  is  of  the  same  form,  and  serves  the  same 
purposes  as  in  field  works;  but,  besides  these,  it  is  indispensa- 
ble sa  a  mask  for  the  scarp  wall,  covering  it  from  distant 
batteries,  in  cases  where  it  rises  above  the  level  of  the  coun- 
terscarp, ami  thus  forcing  the  assailant  to  construct  his  batteries 
along  the  cresl  of  tin-  glacis,  to  obtain  a  position  from  which 
the  scarp  wall  ran  be  breached.  When  the  glacis  serves  only 
mask,  and  to  bring  the  assailant,  as  he  rushes  forward  in 
an  open  assault,  better  under  fire,  it  is  brought  in  so  as  to  rest 
on  top  of  the  counterscarp  wall.  But  in  cases  where  a  covered 
communication  is  needed  beyond  the  ditch,  the  glacis  is  thrown 
outward  far  enough  to  leave  the  requisite  space  between  it 
and   the  counterscarp.     This  sheltered  position  is  termed  the 


4 


COMPONENT  ELEMENTS  OE  PERMANENT  WORKS.       ."-7 

covered-way.  It  servos  both  for  the  circulation  of  the  troops, 
from  point  to  point,  and  as  a  defensive  position  ;  the  pert  of  the 
glacis  facing  the  covered-way  being  arranged,  for  this  latter 
purpose,  like  an  ordinary  earthen  parapet. 

55. ..Mounds  of  earth  which  are  formed  solely  with  a  view  to 
mask  a  scarp  Avail  from  fire  are  termed  fa  ■•  covt  rs.  They  may 
be  either  in  the  form  of  a  glacis,  or  receive,  on  each  sid<\  the 
slope  which  the  earth  would  naturally  take,  sufficient  height 
and  thickness  being  given  to  them  to  subserve  the  object  to  be 
attained. 

56. ..Among  the  modifications  of  the  usual  profile  is  the  one 
represented  in  PI.  3,  Fig.  11,  where  the  scarp  wall,  rising  Only 
t<>  the  level  of  the  site,  is  surmounted  by  a  parapet  wall,  I), 
which  covers  a  ohemi^rde-rondes,  C.  This  parr  of  the  work  is 
termed  &faus8i  -/</•■//< .  By  dividing  the  entire  height  of  scarp 
wall  into  two  parts,  thus  rendering  each  more  accessible  to  an 
open  assault,  and  by  exposing  the  troops  in  it  to  injury  from 
the  splinters  from  the  scarp  wall  behind  them,  caused  by  the 
tin-  of  the  a.-sailant,  the  fausse-braie  has  fallen  into  disuse. 

*>7...The  introduction,  within  the  last  thirty  years,  of  the 
barbette  gun-carriage,  now  in  general  use  for  permanent  works, 
has  led  to  a  modification  in  the  form  of  the  profile,  with  a  view 
of  better  adapting  it  to  the  new  carriage.  This  change  is 
shown  in  PI.  3,  Fig.  4^  and  consists,  mainly,  in  raising  the  level, 
(1  r,  <it'  tlir  terreplein  fifteen  inches,  placing  it  thus  at  six  feet 
nine  inches  below  the  interior  crest,  for  a  distance  of  twenty 
feel  back  from  this  crest,  and  connecting  it  by  a  slope,  •■>/.  of 
45°  with  the  level  bel<>w;  the  parapet  receives  an  interior  slope, 
//  y.  of  1.*)°,  which  falls  upon  a  banquette, /\/,  for  infantry,  the 
tread  of  which  is  two  feet,  and  is  placed  at  four  feet  six  inc 
below,  //.  the  interior  crest.    The  banquette-slop<  .  two 

to  one  perpendicular,  and  tails  upon  the  raised  portion, 
<1  < .  of  the  terreplein.  When  it  is  necessary  to  place  guns  in 
battery  along  any  portion  of  a  parapet  having  this  form  of 
profile,  the  interior  slope  U  cut  down,  nearly  perpendicularly, 
t<»  the  level  of  the  raisi  d  portion  of  the  terreplein,  and  fit 


™» 


& 


i  i  !  HEN  r8  OF    l'KKMANl  NT   W0BX8, 

with  fascines ;  the  earth  between  tibia  raised  portion  and  the 
new  interior  Blope  being  removed,  a  Level  and  solid  bed  is 
the  carriages.  The  surplus  earth  that  lias  to 
l,r  removed  by  this  operation  can  be  used  for  ordinary 
traverses,  and  for  increasing  the  height  of  the  merlons  when 
tin-  parapet  ia  pierced  for  embrasures. 

58...The  dimensions  and  forms  of  the  different  parts  of  the 
profile  are  so  established  as  to  afford  security  against  an  open 
.It ;  sufficient  command  of  the  parapet  over  the  exterior 
ground  to  BWeep  it  effectually  by  its  fire;  cover  from  the  fire 
ot  tin-  assailant  ;  and  ample  room  with  suitable  arrangements 
for  the  delivery  of  the  fire  of  the  assailed. 

.'.:<..>,  \i;r.  A  scarp  wall,  30  feet  high,  is  usually  admitted 
a-  a  sufficient  protection  in  dry  ditches  against  an  escalade. 

This  rule,  drawn  from  the  experience  of  sieges,  and  the 
opinions  of  the  most  eminent  engineers,  seems  a  safe  one; 
since  to  scale  a  wall  of  this  height  would  require  ladders  of 
sufficient  length  to  enable  the  men  who  ascend  to  step  from 
the  ladder,  when  planted  securely  against  the  wall,  ou  the 
Doping,  and  of  sufficient  strength  to  hear  the  weight  of  six  or 
eight  men  mounting  together. 

To  carry  forward  ladders  of  the  dimensions  requisite  for  this 
purpose  and  place  them  ill  position,  with  that  promptitude 
upon  which  the  success  of  an  open  assault  must  mainly 
depend,  Mould,  of  itself,  be  an  operation  of  no  slight  difficulty; 
but,  when  it  is  considered  that  the  assailants  are  exposed  to  the 
lire  of  the  defences  before  reaching  the  ditch,  which  from  its 
width  and  depth  alone  renders  it  a  serious  obstacle,  and  that 
after  they  have  entered  the  ditch  they  are  still  under  the  fire 
by  which  it  is  flanked,  it  is  difficult  to  imagine  how  the  at- 
tempt could  succeed  if  the  assailed  offer  even  an  ordinary 
degree  of  resistance. 

60...For  wet  ditches  filled  to  the  depth  of  six  feet,  and  thus 
secured  from  being  passed  by  fording,  a  height  of  scarp  of  24 
feet  is  < sidered  sufficient  security  from  an  open  assault. 

til. ..Solid  .-ear])  walls,  with  ordinary  counterforts,  I),  receive 


COMPONENT   ELEMENTS  OF    PERMANENT    WORKS.  39 

the  thickness  requisite  to  sustain  the  pressure  of  the  earth  rest- 
ing against  their  hack.  The  batter  given  them  on  their  face 
varies  in  different  services.  In  Vauhan's  profiles  the  hatter  is 
5-1,  or  five  perpendicular  to  one  hase.  In  Oormontaingne's  it 
is  6-1.  But  from  the  effects  of  time,  as  observed  in  the  works 
built  by  these  engineers,  the  slopes  of  their  walls  are  too  great. 
In  the  French  service,  a  slope  of  20-1  is  now  usually  given. 
In  the  Austrian,  12-1 ;  and  in  our  own,  from  24-1  to  48-1.  In 
this  diversity  of  practice  it  is  only  necessary  to  remark,  that 
the  steeper  walls  are  better  protected  from  the  effects  of  the 
weather,  and  tin's  is  a  very  important  consideration  in  struc- 
tures demanding  great  durability. 

62. ..Parapet.  The  essential  properties  of  the  parapet  are 
to  afford  cover,  and  facilities  for  sweeping  the  ground  exterior 
to  it  by  the  artillery  and  musketry.  Its  form  and  dimensions 
arc  therefore,  so  adjusted  as  to  fulfil  these  requirements. 

63. ..For  the  service  of  the  artillery,  barbettes  are  constructed 
behind  the  parapet,  and  suitably  arranged  either  for  guns 
mounted  on  the  ordinary  traveling  carriages,  or  upon  the 
traversing  carriages,  which,  within  some  years  back,  have 
been  introduced  for  the  armament  of  land  and  sea-coast  fronts; 
and  embrasures  are  pierced  in  the  parapet  for  like  purposes. 

84... As  the  sole  of  the  embrasure  is  usually  not  more  than 
three  feel  below  the  superior  slope,  and  generally  parallel  to 
it,  care  must  be  taken  so  to  adjust  its  position  with  respect  to 
the  coping  of  the  scarp  wall  that,  when  the  guns  are  fired 
under  the  same  depression  as  the  superior  dope,  the  balls 
shall  clear  the  edge  of  the  Coping  sufficiently  to  prevent  its 
being  injured  by  negligent  firing.  This  requirement  will 
e  to  determine  the  least  height  of  the  parapet  above  the 
coping,  and  which  may  be  done  by  either  of  the  following 
methods. 

66. ..Supposing  the  parapet  to  be  formed  of  earth  of  the  or- 
dinary  character.  PI.  4,  Fig.  14,  in  which   the   natural   slop 
45°,  or  1-1 :  the  superioi  slope,  which  is  the  san  i1  of 

the  embrasure  sole,  is   !-«'•,  the  one  usually  adopted  as  the 


PI  KMAN;   N  1     WORKS. 

•  for  the  parapets  of  permanent  work-:  the  thicknee 
tin-  parapet  iv  feet,  the  least  given  to  it  to  resist  the  heavi 
calibre  thus  far  employed}  and  that  a  berm  of  two  feet 
allowed  on  the  top  of  the  Bcarp  wall,  between  the  edge  of  the 

ing  and  the  foot  of  the  exterior  slope:  let  a  horizontal  line, 
.  be  first  drawn  at  the  level  of  the  coping)  and,  from  its  ex- 
terior edge,  ".  a  second  line,  </  c,  making  an  angle  of  1-6  with 
a  //,-  this  hist  line  will  be  the  direction  of  a  shot  tired  under 
tin'  depression  of  1-6,  which  would,  just  graze  the  edge  of  the 
coping,  and  may  be  assumed  as  the  lowest  position  that  the 
of  an  embrasure  can  receive;  a  line,  therefore,  drawn 

.lid  to  it  c  and  ."-  feet  above  it.  will  be  the  lowest  position 
also  of  the  superior  slope.  It'  a  line  is  now  drawn  through  a, 
the  interior  edge  <>f  the  berm  and  the  fodt  "t"  the  exterior  slope; 
making  an  angle  of  J-l  with  a  b,  it  will  be  the  direction  6f  the 
exterior  slope;  and  the  point  m,  where  it  cuts  the  direction  of 
the  superior  Blope,  will   he   the   exterior    creSt    of   the   para] iet . 

Setting  off  along  the  horizontal  line  through  m  the  thickness 

of  the  parapet,  or  ix  feet,  and  erecting  a  vertical  at  the  point 

thus    determined,   the    point   //,    where   this  vertical    cuts   the 

superior  Blope,  will  give  the  position  of  the  interior  exeat,  », 

and,  consequently) will  determine  its  vertical  height  above  the 

ing. 

66. .. The.  following  simple  calculation  will,  in  like  manner, 

give  the  same  result.     Denote  by  x  the  base  <  </—</  m  of  the 

rior  Blope.     As  the  berm  */  <  =2  feet,  the  thickness  of  the 

parapet  d  b     1 v  fed  ;  the  distance  ''  U—a  e+e  (/+</  l>='2'+x+ 

l&'=x  +  '2"' :  hut  since  the  line  <i  <■  makes  an  angle  of  l-<!  with 

</  />.  the  point  .-.  where   it    cuts   the  vertical   through  '/,  will 

make  b  0=1-0  a  J,  and,  as  from  the  position  of  the  superior 

slope    ami    the    thickness,    1N   feet,    given   to   the    parapet,  the 

point  //  is  three  feet  above  the  points  ///  and  <•.  it  follows  that 

</  ///  =  ,r.     Therefore,    from    the    two    preceding   equations 

there  obtains  .<•— l-t;  (x+Qtf);  hence  x=±  feet.  Prom  this 
value  of  ,;,  the  height  b  oof  /<,  ahovs  the  point  a,  is  7  feet  ; 
which,  under  the  assumed  conditions,  is  the  least  height  of  the 


COMPONENT   ELEMENTS  OF   PERMANENT   WORKS.  41 

interior  crest  above  the  coping  in  which  a  ball,  passing  in  the 
same  line  as  the  sole  of  the  embrasure,  would  just  touch  the 
exterior  edge  "f  the  coping.  In  order  to  secure  the  coping 
from  damage,  the  interior  crest  is  placed  8  !'<•<■!  above  it. 

It  should  he  observed  thai  flic  result  here  arrived  at,  being 
dependent  on  the  assumed  data,  will  vary  by  changing  the 
elements  of  the  problem. 

ST.. .The  height  of  s  feet  thus  determined,  as  the  least  which 
the  parapet  should  receive  above  the  magistral,  is  advanta* 
geous  both  as  to  economy  ami  for  the  defence,  and,  therefore, 
should  not  be  exceeded  except  fur  good  reasons.  This  will 
be  apparent,  when  it  is  considered  that  the  pressure  on  the 
scarp  wall,  from  the  weight  of  the  parapet,  increases  with  the 
height  of  the  latter,  and  that  the  wall  must  he  made  stroo 
in  proportion  ;  and.  although  an  increased  height  of  parapet, 
by  increasing  the  obstacle  to  an  escalade,  is  in  favor  of  the 
defence,  still,  when  it  much  exceed:,  g  feet,  the  assailant,  on 
reaching  the  top  of  the  wall,  will  find  shelter  from  the  fire  of 
the  parapet,  which  will  pass  above  his  head,  and  he  will  be 
better  enabled  to  reach  the  top  of  the  parapet  than  when 
partly  exposed  to  this  tire,  as  he  will  be  in  low  parapets. 

•'.v.. The  inclination  of  l-»i  has  been  generally  adopted  as  the 
•e.-t  inclination  of  the  superior  slope,  both  on  account  of 
the  greatest  depression  that  guns  can  be  fired  under  without 
straining  too  much  tin,'  carriages,  and  to  avoid  making  the  por- 
tion of  the  parapet  near  the  interior  crest  BO  weak  that  itcould 
be  readily  destroyed,  and  the  troops  and  materiel  exposed  to 
view.  When.  \  <  r  the  held  of  tin-  will  admit  of  it,  it  will 
prove  advantageous,  under  these  two  points  of  view,  to  gii 
smaller  inclination  to  the  superior  slope.     In  ca-es  where  it  is 

able  to  reach  Borne   point,  by  the  tire  requiring  a 
slope  than  I-'!,  it  may    be   done   without    inconveni  the 

parapet  is  not  likely  to  f.  d  to  a  heavy  fir  ible 

inclination  being  also  given  t<»  the  gun-platform. 

terior  slop-,  for  the   i  in  disi 

the  parapets  of  field  works,  should  not  be  land  fin 

•; 


■!:_'  ELEMENTS  OF    PERMANENT    WOBXfl. 

than  the  natural  Blope  of  the  earth  of  which  the  parapet  is 
formed.     In  I   works,  where  the  parapet  i>  hiirh,  and 

be  reached,  within  cannon  range,  only  by  elevating  the 
guns  of  tin-  ships,  the  exterior  slops  may  be  replaced  by  a 
vertical  revetement  of  stone,  or  one  oi  Bods  with  but  a  slight 
inclination,  as,  from  the  direption  of  the  lire,  this  facing,  even 
it'  partially  destroyed,  will  not  cause  Buch  weakness  in  the 
parapet  as  to  expose  the  troops.  By  using  a  facing  of  this 
kind,  the  parapet  will  occupy  Less  room  and  Leave  more  interior 
.  which,  in  small  works,  is  often  desirable. 

7". ..A.-  a  berm  of  two  feet  affords  a  tolerable  landing  to  the 
hint  in  an  escalade,  it  would  he  hitter  to  make  it 
particularly  on  fronts  open  to  Bach  an  assault.  Tin-  usual 
berm  may  It  given  when  the  work  is  constructed,  and  he  after- 
ward Lessened  by  increasing  the  thickness  of  the  parapet  when 
tin-  work  is  to  he  placed  in  a  defensive  attitude. 

71. ..The  thickness  of  the  parapets  of  ordinary  earth  seldom 
exceed  30  feet.  This  is  the  dimension  usually  given  in  Euro- 
pean constructions  of  important  works  liable  to  a  long  expo- 
sure- to  lire,  and  has  luen  found,  by  experience,  to  afford  good 
i-  against  a  well-nourished  and  protracted  tire  of  the 
heaviest  calibre  thus  far  \\>vA.  In  our  service,  a  thickness 
lv  feet  has  been  more  usually  given.  For  less  important 
works,  and  particularly  when-  parapets  arc  not  likely  to  he 
systematically  battered,  the  thickness  may  be  safely  reduced 
to  L2  or  IT)  l'( «  t. 

72.. .In  the  form  of  profile  given  in  PL  3,  Fig.  4,  the  portion 
of  the  terreplein  on  which  the  guns  rest  in  battery  is  placed 
it  a  level  below  the  interior  crest,  to.  admit  the  guns  being 
tired  over  the  parapet  ;  and  this  difference  of  level  is  sufficient 
t..  give  good  cover  along  the  parapet  to  the  men  serving  the 
guns.  The  portion,  b  <\  <<\'  the  terrepleiu  to  the  rear  of  this 
a  communication  along  the  line  of  fortification,  and, 
being  further  hack,  should  he  Bomewhat  Lower,  to  afford  good 

or  fr shot  just  passing  over  the  interior  crest.     It  is  osu 

ally  placed  at  a  level  of  8  feet  below  the  interior  crest ;  aslope 


** 


COMPONENT   ELEMENTS  OF   PERMANENT   Works.  43 

of  one  foot  inward  being  given  to  it,  estimating  it  from  the  line  of 
the  interior  crest  to  the  exterior  edge  of  the  terreplein;  to  free 
it  rapidly  from  the  rain-water.  This  level,  however,  may  !>c 
lowered  if  the  irregularity  of  the  site  requires  it,  from  the 
command  the  exterior  ground  may  have  over  the  work.  In 
all  cases  it  will  be  rather  a  question  of  economy,  to  be  decided 
by  the  amount  of  excavation  and  embankment.  As  the  space 
in  question  serves  chiefly  the  purposes  of  a  communication,  it 
may  be  reduced,  through  motives  of  economy,  to  a  width 
which  will  be  sufficient  for  the  gun-carriages  arid  other  ve- 
hicles employed  in  the  defence  to  pass  each  other.  For  this 
purpose  the  entire  width  of  the  terreplein,  estimating  it  be- 
tween the  verticals  through  the  interior  crest  of  the  parapet 
and  the  crest  of  the  rampart-slope,  has  usually  received  42 
feet  in  enceintes  of  importance  where  a  circulation  of  the  kind 
just  mentioned  is  to  be  provided  for.  In  other  cases  it.  may 
be  reduced  to  24,  or  even  20  feet.  It  should  be  remarked, 
however,  that,  as  a  wide  terreplein  facilitates  the  disposition  Of 
troops  for  an  active  defence  of  the  breach,  it  should  not  he  too 
much  reduced  along  those  portions  of  the  enceinte  exposed  to 

he  opened. 

..The  rampart  toward  the  parade  usually  receives  a  slope. 
greater   than    that   which    the   earth   would   naturally  assume 
where  the  interior  space  admits  of  it.     This  will  offer  the  means 

of  forming  narrow  foot-paths  along  this  slope  leading  from  the 
parade  to  the  terreplein  at  convenient  points,  and  prevent  the 

slope  from  being  injured,  which   it    is   apt    to    he    hy    the    men 

ping  such  Bhort   cuts  for  thee  Where  the  int. 

Bpace  would  he  too  much  circum.-crihed.  this  slope  may  b< 

placed  by  a  parade  wall. 

71. ..The  banquette-tread  and  the  interior  shown  in 

PL  i  I.  will    answer   sufficiently    well    for  ordinary   pur- 

poses; hut  where  a  warm  tire  in  two  ranks  is  to  be  sustained, 
the  interior  slope  should  be  trimmed  down  to  the 

■■  Inch  will,  at  tie 

banquette-tread  so  ai  two  rank.-..     It  would  he  well. 


C"* 


■l^fu 


V 


11  COMPONENT    ELEMENTS  OT    PEEMANENT    works. 

also,  in  making  these  changes  for  an  active  defence,  to  raise  the 
banquette-tread  bo  within  a  tevelof4j  feet  of  the  interior  en 
for  tin'  greater  convenience  of  short  men  in  delivering  their 
fire. 

7.  ...V  d  <'t'  the  parapet  over  the  site  has  a  very 

important  bearing  in  the  defence  of  permanent  works,  as  the 
ilanf  meets  with  the  more  difficulty,  in  running  forward 
his  trenches,  as  the  fire  of  the  defences  becomes  more  plung- 
ing. Motives  of  economy,  however,  require  the  command  to 
be  restricted  within  quite  narrow  limits.  When  the  work  con- 
sists of  a  simple  enceinte,  enveloped  by  a  covered-way,  the 
command  may  be  reduced  to  16  feet,  allowing  a  command  of 
s  feet  to  the  interior  crest  of  the  glacis  over  the  site,  and  a 
height  of  8  feel  to  the  interior  crest  above  the  coping,  which, 
with  the  rest  of  the  scarp  wall,  to  be  masked  by  the  glacis, 
musl  not  rise  above  the  level  of  its'  interior  crest.  Where 
there  are  other  outworks  besides  the  covered-way  in  defensive 
relations  with  the  enceinte,  the  latter'  cannot  receive  a  com- 
mand over  the  site  of  less  that  about  20  feet,  in  order  to  give 
it  a  suitable  command  over  the  whole  of  the  outworks. 

7<i...('or.\'ri:i:scAi;i>  Wall.  A  revetted  counterscarp  is  re- 
garded as  adding  to  the  difficulty  of  descending  into  the  ditch, 
and  as  offering  greater  security  against  an  open  assault.  For 
this  purpose  the  wall  should  not  be  less  than  12  or  15  feet  in 
height,  to  oiler  a  serious  impediment;  in  any  case  where  mo- 
tives of  economy  do  not  imperiously  demand  it,  the  countcr- 
BCarp  wall  of  the  enceinte  should  be  from  18  to  21  feet  in 
height.  This  height  will  not  only  give  great  security  to  the 
ditch,  but,  as  will  be  seen  in  the  description  of  the  siege  works 
of  tlu'  assailant,  it  will  delay,  considerably,  his  progress,  as 
the  gallery  by  which  he  must  generally  reach  the  bottom  of 
the  ditch  from  the  level  of  the  covered-way  terreplein,  is  one 
of  the  slowest  and  most  laborious  of  his  operations. 

7T...I)ii(  ii.  The  width  and  depth  of  the  enceinte  ditch  de- 
pends mainly  upon  the  amount  of  embankment  required  for 
the  enceinte  and  the  glacis,  and,  therefore,  will  result  from  the 


COMPONENT   ELEMENTS  OF    PERMANENT   WORKS.  \~> 

calculation  for  equalizing  the  excavation  and  embankment 
which  these  demand.  A  deep  and  narrow  ditch  offers  the  ads 
vantage  of  presenting  more  difficulty  to  the  assailant  in  reaching 
the  bottom  of  it  ;  and,  from  the  position  he  is  obliged  to  take  up 
for  his  breach  batteries  to  open  the  scarp  wall,  his  fire  cannot 
Bee  the  wall  so  near  its  foot  as  in  a  wide  ditch,  and  the  breach, 
therefore,  may,  from  this  cause,  be  less  practicable.  A  wide 
ditch,  on  the  other  hand,  requires  more  lahor  to  construct  the 
trench  across  it,  by  which  the  assailant  can  reach  the  foot  of 
the  breach  undercover.  This  is  a  consideration  of  some  im- 
portance in  wet  ditches,  where  the  assailant  is  obliged  to  con- 
struct a  dike,  upon  which  the  parapet  of  his  cover  is  placed. 
In  the  practice  of  engineers  the  enceinte  ditch  has  received  a 
width  of  from  $0  u>  80  yards  when  dry,  and  from  30  to  45 
yards  when  wet.  These  dimensions  may  he  reduced  to  within 
10  or  L2  yards,  where  the  embankments  are  not  great,  and  cir- 
cumstances an'  unfavorable  to  an  attempt  at  escalade. 

7*. ..The  bottom  of  the  ditch  usually  receives  a  Blight  slope 
iron i  the  foot  of  the  scarp  and  counterscarp  to  its  centre, 
where  a  small  drain,  termed  a  OUnetfa,  is  dug  to  receive  the 
surface  water  and  keep  the  ditch  dry.  In  BOtne  cases,  from 
motives  of  economy,  the  difference  of  level  hetween  the 
cunette  and  the  foot  of  the  counterscarp  walls  is  increased) 
thus  giving  a  l<  bs  height  of  wall.  This  practice,  however,  can 
only  be  followed  where  the  foundations  of  the  wall  will  be 
secure  from  the  soil  of  the  bottom  of  the  ditch  being  of  such  a 
nature  as  not  to  yield  from  the  effects  of  the  weather  upon  it. 

79...Geneeal  Remarks.  The  rule- here  given  with  respect 
to  the  form  and    dim  of  the  general   profile  of  till 

ceinM  are  founded  upon  reasons  growing  out  of  the  nature  of 
the  question,  and  as  -uch  have  Berved  a>  guides  to  engii 
in  the  practice  of  their  profession.  A.a  they  have  stood,  he- 
side.-,  the  test  of  long  experience,  i1  follow  them, 
whilst  at  the  same  time  the  engineer  should  not  heeitat 
vary  from  them  when  satisfied,  afl  ul  examination,  that 
the.            fore  him  requires  it.     Fortification,  it  mutt 


46  OOMPOH  PERMANENT   WORKS. 

membered,  is  like  all  other  arts.  It  has  its  canons  which  are 
founded  upon  the  nature  of  the  question,  and  its  rules  of  prac- 
tice based  upon  these  and  upon  experience.  As  the  latter  pre- 
sents i"  the  engineer  new  tacts,  his  practice  must  be  made  to 
conform  to  them,  hut  the  general  principles  oi  his  art  must 
ever  remain  the  Bame  and  be  his  invariable  guide. 

OPEN  DEFENCES. 

80...Bj  this  term  is  understood  the  dispositions  made  for  the 
action  of  the  troops  and  armament  which  are  covered  from  the 
misajles  of  the  assailed  by  the  parapet  alone. 

Bl...To  this  class  belongs  the  arrangement  of  the  parapet 

which  has  already  been  described;  simple  looj>-lu>lil  walls  for 
musketry,  used  as  enclosures  of  gorges,  etc.;  e.ctrri<>r  corridors 
which  are  covered  either  by  a  wall  or  an  earthen  parapet; 
and  "barbettes  and  embrasures  for  artillery. 

82...LoOP-BOLED  Walls.  Walls  of  this  class  when  used  as 
the  enclosures  of  the  gorges  of  lunettes  or  other  isolated  works, 
placed  in  advance  of  the  enceinte,  but  within  the  reach  of  its 
artillery  fire,  should  be  high  enough  to  secure  the  work  from 
an  open  assault,  and  sufficiently  thick  to  resist  the  occasional 
shot  which  may  reach  them  over  the  parapet  by  which  they 
are  covered.  For  these  purposes  the  height,  PL  4',  Fig.  24, 
should  be  from  12  to  15  feet,  and  the  thickness  from  4  to  5 
feet.  The  loop-holes  arc  not  placed  nearer  to  each  other  than 
from  3  to  4  feet,  estimated  between  their  axes.  They  should 
be  at  least  6  feet  above  the  exterior  foot  of  the  wall,  and  4J 
feel  above  the  ground  or  banquette  within.  The  loop-holes 
are  usually  placed  at  regular  intervals  along  the  line  ef  the 
Wall;  or  only  opposite  that  portion  of  the  exterior  ground 
upon  which  a  fire  is  to  be  brought  to  bear. 

83. ..The  form  and  dimensions  of  the  loop-hole  will  depend 
upon  the  thickness  of  the  wall  and  the  field  of  view,  both  ver- 
tically and  horizontally,  which  is  to  be  covered  by  its  fire. 
The  plan   is  either  trapezoidal,  PI.  4,  Figs.  17,  20,  widening 


COMPONENT    ELEMENTS   OF    PERMANENT   WORKS.  47 

from  the  front  of  the  wall  inward,  or  else  it  widens  from  the 
centre  each  way  to  the  front  and  back;  or,  as  is  the  more 
usual  form  in  our  works,  the  interior  portion  from  the  centre 
widens  inward,  whilst  the  exterior  part  is  rectangular  in  plan. 
The  first  form  is  best  adapted  to  walls  not  more  than  2$  feet 
thick;  the  others  to  heavier  walls;  the  object  being  to  lessen, 
as  far  as  practicable,  the  weakness  which  loop-holes  necessarily 
cause  to  the  wall;  this  defect  increasing  as  the  exterior  or 
interior  opening  is  greater. 

84.. .For  thin  walls,  where  the  plan  of  the  loop-hole  is  tra- 
pezoidal, the  width  of  the  exterior  opening  may  be  from  2  to 
4  inches,  and  that  of  the  interior  from  15  to*  18  inches.  These 
dimensions,  however,  may  vary  according  to  the  field  of  fire 
to  be  brought  within  the  range  of  the  loop-hole,  the  more  or 
less  cover  to  be  given  to  the  troops,  and  the  strength  of  the 
masonry  of  which  the  wall  is  formed.  The  vertical  dimensions 
of  the  loop-hole,  both  on  the  interior  and  the  exterior,  will 
depend  upon  the  field  of  fire  to  be  embraced  in  this  last  direc- 
tion, and  they  will  be  regulated  accordinghT ;  the  slope  of  the 
top  and  sole  of  the  loop-hole  receiving  a  suitable  slope  or 
direction  for  this  purpose. 

The  foregoing  details  can  only  be  well  determined  upon 
from  the  special  object  to  which  the  loop-holed  defences  are  to 
be  applied.  Care  only  is  to  be  taken  that,  in  attempting  to 
give  cover  to  the  troops,  their  ijeld  of  view  be  not  too  restrict- 
ed, by  too  narrow  an  opening  for  the  use  of  the  iire-arms. 

85...Wnere  the  throal  or  narrowest  part  of  the  loop-hole  is 
within  the  wall,  the  exterior  opening  leaves  a  wider  mark  for 

the  missiles  of  the  assailed'  and  when  the  sides  of  the  loop- 
hole gradually  widen  outward  a  .-hot  striking  .me  of  them  may 
glance  inward  and  do  injury.  To  prevent  this  accident  'lie 
sides  and  sometimes  the  Bole  are  made  in  offsets.  This,  how- 
ever. [|  not  so  convenient  a  mode  of  constructing  the  loop- 
hole, nor  one  so  efficient  in  arresting  the  shot  which  do  not 
directly  attain  the  throat,  a.-  the  one  in  PI.  A.  big.  1.  which  is 
the  plan  of  one,  taken   from  our  works,  pierced   in  a  wall  o" 


•poMAT    ri. l  M  PERMANENT    WOBKf. 

feet   thick.    The   plan   of  the  exterior  portion,  a,  is  rectan- 
gular, the  exterior  width  2  feet;  the  throat  is  at  the  centre  of 

tlie  wall,  ami  6*  wide;  the  interior  portion,  $,  is  trapezoidal, 
and  _  feet  wide  <>n  the  interim-. 

..In  open  exterior  corridors  the  loops  are  covered  in  front, 
either  by  an  earthen  parapet,  which  is  usually  only  musket- 
proof,  the  scarp  wall  being  run  up  to  the  superior  Blope,  or 
the  Bcarp  wall  serves  as  the  cover,  in  which  case  it  is 
pierced  either  throughout  its  Length  or  at  suitable  points  with 
loop-holes.  The  floor  of  the  corridor,  C\  PI.  4-,  Fig.  27,  serves 
as  a  banquette-tread  for  the  loop-holes,  and  is,  therefore, 
placed  with  reference  to  the  direction  of  the  fire  from  the  Loop* 
holes.  The  height  at  which  the  scarp  wall  rises  above  the 
floor  of  the  corridor  will  depend  upon  the  level  of  the  floor 
and  that  of  the  bottom  of  the  ditch;  this  height,  however, 
Bhonld  not  be  less  than  6£  feet,  to  afford  sufficient  cover  to  the 
troops. 

87.. .Scarp  walls  of  this  arrangement  are  termed  semi-de- 
tacked,  to  distinguish  them  from  the  ordinary  retaining  scarp 
walls  and  those  in  which  the  wall  is  entirely  separated  from 
the  rampart,  serving  as  a  simple  enclosure  to  it  to  prevent  an 
escalade, 

88.. .The  preceding  Figure  is  given  as  an  example  of  a  semi-de- 
tached M-arp,  A,  an  earthen  counterscarp,  and  covered-way, 
D  ;  being  a  section  of  an  outwork  of  one  of  our  sea-coast 
forts. 

Mi...  I! ak]5Ette  Batteries.  For  guns  mounted  on  the  ordi- 
nary held  and  siege  carriages,  the  barbettes  are  constructed 
in  the  same  manner  and  with  the  same  dimensions  as  in  field 
works.  The  arrangement  of  the  ramps  and  slopes  being  deter- 
mined by  the  position  in  which  the  barbette  is  placed,  and  its 
relative  position  with  respect  to  the  terreplein  and  parapet. 

0O...FoT  the  heavy  guns  used  in  forts,  both  for  sea  and  land 
fronts,  a  solid  foundation  of  stone  is  laid  to  receive  the  pintle 
and  rail,  upon  which  the  chassis  of  the  gun  is  made  to  tra- 
verse*    This  foundation  consists  of  a  heavy  block,  set  firmly  in 


COMPONENT    ELEMENTS  OF    PERMANENT   WORKS*  li' 

abed  of  beton,' to  which  the  pintle,  placed  at  the  centre  of 
motion,  is  solidly  attached;  and  of  stone  blocks  set  in  like 
manner,  to  which  arc  firmly  attached  the  iron  rails,  which 
cither  form  a  segment  of  a  circle,  as  in  PL  7,  Figs.  54-,  55,  or  a 
complete  circle^  as  in  iFigs.  56,  57,  58,  upon  which  the  tra- 
verse-wheels  ran. 

91. ..In  order  to  afford  the  gun  a  wide  traverse,  a  recess  is 
made  in  the  parapet  in  front  of  the  carriage,  of  sufficient 
dimensions  to  allow  the  manoeuvres  of  the  chassis  and  top  car- 
riage without  obstruction;  for  this  purpose  it  has  received  a 
depth  of  "2  feet,  its  front  5  feet;  its  two  sides  having  a  slant  of 
.'in  inches  base  to  24  indies  perpendicular,  The  recess,  and 
Usually  the  entire  length  of  the  battery  front,  is  faced  with  a 
breast-height  wall  that  only  rises  to  within  18  inches  of  the 
top  of  the  parapet;  its  thickness  being  2  feet.  The  Figures 
referred  to  give  the  plan,  sections  and  elevation  of  the  barbette 
arrangements  in  question  adopted  in  our  service. 

92... Embrasure  Batteries.  The  embrasures  cut  in  the  para- 
pets for  -mis  on  field  and  siege  carriages,  differ  in  no  essential 
point  from  those  for  field  works.  It  is  well,  however,  to  ob- 
serve, as  the  parapet  is  weakened  by  receiving  embrasures,  the 
Bplay  given  to  them  should,  in  all  cases,  be  carefullv  regulated 
by  the  held  of  fire  it  is  desirable  to  command,  so  as  to  Leave 
"as  large  a  mass  of  merlon  between  each,  as  practicable,  to 
ailant's  fire. 

93... For  guns  mounted  on  sea-coast  carriages  the  embrasures 
are  very  shallow,  merely  covering  the  gun  from  lateral  view. 
PL  A,  Fig.  2  is  a  profile  of  the  enceinte  through  the  axis  of 
an  embrasure  of  r<  cent  French  works,  showing  the  manner  in 
which  the  profile  is  modified  and  revetted  for  the  servi© 
the  pie© 

'.tb..M  \<  nir.'iu-.  For  the  purpose  of  attaining,  by  mus- 
ketry, the  foot  of  a  scarp  wall  without  flank  defences,  resort 
must  be  had  to  S  machiconlated  arrangement  at  the  top  of  the 
Bcarp. 

nal    mode    adopted    for   this   purpose,  PL  v.   1 

7 


.".'i  :.""MM    i  i.i  mi  n  is  OF   PERMANENT   WORKS. 

»;;.  |  form  a  parapet  wail,  which   rests  upon  a  wlid 

horizontal  band  of  Btone,  mar  the  top  of  the  scarp,  which  is 
supported  on  corbels,  or  projecting  blocks,  firmly  built  into 
the  wall.  The  back  of  the  parapet  wall  is  placed  a  few  inches 
in  advance  of  the  scarp,  leaving  room  for  die  slanting  loop- 
holea  pierced  in  the  horizontal  band  through  which  the  lire  is 
to  be  delivered  on  the  toot  of  the  scarp.  The  top  of  the  para- 
pet wall  is  also  arranged  to  admit  of  firing  on  more  distant 
points. 

!•<;.. .In  the  example  given,  which  is  from  an  Austrian 
authority,  Fig.  07  is  a  front  elevation,  and  Fig.  OS  a  section 
through  a  loop-hole. 

Figs.  *!.'),  fit!,  are  a  front  elevation,  and  section  through  a 
Loop-hole,  from  the  same  authority.  This  is  a  semi-detached 
scarp  wall,  the  top  portion  of  which  is  arranged  on  the  back 
with  loop-holed  recesses;  the  lower  portion  having  very  in- 
clined arched  recesses  in  front,  with  slanting  loop-holes  to  tire 
on  the  foot  of  the  scar])  from  the  upper  recesses. 

97. ..Whore,  from  the  irregularity  of  the  site,  tlfe  ordinary 
machicoulis  cannot  be  made  efficient,  resort  may  he  had  to 
small  polygonal  chandlers  of  stone,  open  at  top,  and  having 
the  sides  and  bottom  pierced  with  loop-holes  and  machicoulis. 
These  constructions  may  he  made  just  of  sufficient  size  to  hold 
a  .-ingle  sentinel.  They  are  placed  at  the  angles  of  the  works, 
where  they  will  not  be  exposed  to  artillery,  and  are  supported 
on  a  corbel  work  projecting  from  the  top  of  the  scarp  wall. 

COVERED  DEFENCES. 

98...Dktacui:!>  Scarp  Walls.  When  the  scarp  walls  are 
entirely  detached,  leaving  an  open  corridor  between  them  and 
the  rampart,  they  are  pierced  with  one  or  two  tiers  of  loop- 
holes from  which  a  fire  can  be  brought  from  the  ditch  and 
upon  the  terreplein  of  the  covered-way,  or  any  work  in  front 
of  the  enceinte. 

99.. .To  give  cover  to  the  men  at  the  loop-holes,  arched  re- 


COMPONENT    ELEMENTS   OF    PERMANENT    WORKS.  51 

cesses,  PI.  4,  Figs.  25,  20,  are  made  in  the  thickness  of  wall, 
ox  else  short  counterforts  arc  built  hack  from  the  Avail  which 
serve  as  the  piers  of  covering  arches.  The  width  of  the  re- 
•s  should  admit  of  three  or  four  loop-holes  at  the  usual 
distance  apart;  their  height  and  depth  be  sufficient  to  give 
the  men  shelter  from  vertical  lire,  and  allow  them  to  handle 
their  arms  with  convenience. 

100. ..The  two  Figures  above  are  sections  of  this  description 
of  scarp  wall  taken  through  the  crowns  of  the  arches,  as  shown 
in  an  Austrian  work.  A,  is  a  section  of  the  wall ;  B  and  Dy 
elevations  of  the  sides  of  the  recess;  C,  an  elevation  and  sec- 
tion of  the  recess  arch. 

101... Semi-detached  walls,  Fig.  2S,  are  also,  in  some  cases, 
built  with  recesses.  Besides  these,  traverse  walls,  Z7,  are  built 
back  from  the  scarp  wall  into  the  parapet,  at  intervals,  to 
afford  cover  to  the  troops,  circulating  in  the  corridor,  from 
enfilading  tire,  and  to  admit  of  a  defence  of  the  corridor  it' 
the  assailant  should  enter  it  between  any  two  of  these  tra- 
verses. For  this  purpose  they  are  pierced  with  loop-holes,  and 
have  door-ways  for  circulation  throughout  the  corridor. 

102... In  the  more  recenl  fortifications  built  in  Germany  and 
the  north  of  Europe,  a  frequent  use  has  been  made  of  detached 
scarps.  They  present  a  double  obstacle  to  an  escalade,  as  the 
lant.  having  gained  the  top  of  the  wall,  has  .-till  to  descond 
ou  the  other  side*  They  would  probablj  be  more  easily 
breached  than  the  ordinary  scarp  revetements  with  counter- 
forts; and  from  some  experiments  made  in  England,  with  a 
view  of  ascertaining  the  resistance  <>t  these  walls  and  the 
r  given  them  by  earthen  masks,  arranged  in  a  manner 
similar  to  -  rman  fortifications,  it  is  questionable 

whether,  with  the  heavier  calibre  now  coming  into  use  in  sit 
and  the  improvement  of  late  year.-  in  their  range,  such  walls 
might  not  be  readily  breached  from  a  distai 

L03.JTh«  partly  detached  scarp  wall,  with  relieving  arches, 
would  seem  to  offer  the  advantage  of  more  security  from 
calade  than  the  old  scarp  wall,  as  the  assailed  are  in  a  better 


:>-J.  ELEMENTS  OF    PERMANENT    WORKS. 

orridor  to  drive  the  assailant  back  than  when 
placed  behind  the  parapet.  It  offers  all  the  difficulties  to 
bn  aching  of  the  full  scarp  with  relieving  arches,  and  presents, 
whm  the  breach  is  rendered  practicable,  a  narrow  defile 
through  which  the  assailant  must  force  his  way  into  the  work; 
whereas,  when  the  wholly  detached  scarp  is  overthrown,  the 
!ant  may  enter  with  any  front  he  may  choose,  as  the  only 
obstacle  then  in  his  way  will  be  that  of  the  height  of  the  ram- 
part and  the  steepness  of  its  exterior  slope. 

1<'-1...S<  aim-  Galleries.  In  the  permanent  works  of  more 
recent  construction  in  our  own  country  ami  in  Europe,  revete- 
ment  Malls,  with  relieving  arches,  PI.  4,  Fig.  15, have,  in  most 
-.  been  introduced  instead  of  the  ordinary  thick  walls,  with 
counterforts,  which  had  been  hitherto  the  usual  mode  of  re- 
taining the  earth  of  the  rampart  and  parapet. 

lo.".. ..The  piers  of  the  relieving  arches,  which  also  serve  as 
counterforts  to  the  revetenient  wall,  are  rectangular  in  plan, 
and  usually  ran  hack  from  12  to  16  feet.  They  are  from  4  to 
t  thick,  and  placed  from  12  to  IS  feet  apart  between  their 
centre  lines.  The  arches  are  usually  full  centre,  and  two  feet 
thick,  with  a  roof-shaped  capping,  which  adds  an  additional 
thickness  from  !♦  to  12  inches  over  the  crown  of  the  arch. 

lot;. ..The  preceding  Figure  is  a  section  of  a  revetement 
wall  of  this  kind,  of  one  of  our  forts,  though  the  curtain  in 
front  of  which  is  a  mask,  of  which  1)  is  the  section.  A\  is  an 
elevation  of  the  face  of  the  pier;  C,  the  relieving  arch;  and 
J,  the  scarp  wall. 

1  < '7.-/11 1 i-  mode  of  construction  offers  the  advantages  of  a 
more  Stable  structure,  and  rendering  it  more  dimcnll  for  the 

assailant  to  make  a  practicable  breach  in  the  wall,  whilst,  by  a 
BUltable  arrangement  of  the  relieving  arches  and  their  piers 
w  ith  the  earth  of  the  rampart,  a  sullicieiil  space  can  be  secured 

behind  the  Bcarp  wall  to  form  a  gallery  for  defensive  purposes. 
l08...The  arches  and  piers  form  the  top  and  sides  of  the  gal- 
lery, the  scarp  wall  forming  the  front,  and  the  back  or  rear 

being  either  partly  or  wholly  closed   by  a  wall  which   retains 


COMPONENT    ELEMENTS  OF    PERMANENT    WORKS. 

the  earth  behind  it.  The  gallery  is  thus  divided  ap  into 
chambers,  Hie  communication  between  which  is  effected  by 
door-ways  made  through  the  piers. 

109.. .The  width  and  heigh*  of  the  gallery  should  in  all  oases' 
be  sufficient  to  allow  the  men  ample  room  tor  handling  their 
fire-arms,  and  to  admit  <>t'  a  circulation  through  the  gallery, 
when  the  troops  for  the  defence  are  posted  in  it. 

1  in. ..From  three  to  tour  Loop-holes  are  made  in  the  portion 
of  the  scarp  wall  that  forms  the 'front  of  each  chamber.  The 
dimensions  and  forms  of  the  loopholes  are  the  same  as  already 
described,  and  they  are  otherwise  arranged  for  defence  as  in 
detached  scarp  Malls. 

111. ..In  PI.  4,  Fig.  1(!,  a  section  of  a  scarp  gallery  cOtt^ 
strncted  in  one  of  our  forts  is  shown.  A,  is  the  scarp  wall; 
B,  the  pier  of  the  relieving  arch,  C ;  I),  the  rear  wall  which 
closes  the  gallery  and  sustains  the  earth  behind  it.  Tlie  sec- 
tion also  .-hows  the  parts  of  the  rampart  and  parapet,  and  the 
breast-height  wall.  /•/. 

1  1  •_'... In  Figs.  17.  Is.  19,  the  plan,  section  and  rear  elevation 
of  a  gallery  is  shown  as  given  in  French  authorities.  The. 
peculiarity  of  this  example,  Fig.  1!',  consists  in  the  arrange- 
ment of  the  rear  of  the  gallery,  which  instead  of  being  en- 
tirely closed  by  a  wall  is  only  partly  so;  a  small  wall,  «, 
which  rests  upon  an  arch,  I,  lmilt  hctween  the  two  pier 
placed  parallel  to  the  hack  of  the  scarp  wall,  and  at  a  distance 
from  it  equal  to  the  width  of  the  gallery,  the  top  of  the  wall 
being  raised  to  the  level  of  the  surface  of  the  earthen  si 
which  falls  in  behind  from. ..the  top  of  the  arch.  The  section. 
1^.  through  r  *,  ami   elevation,  Fig.  L9,  show  the  position 

of  the  loop-holes,  and  the  vent  for  the  escape  of  the  stftoke, 
which  i>  pierced  in  the  scarp  wall  just  below  the  crown  of  the 
arch.     By  are  th<  be  arches  with  their  capping;  Ik 

the  door-ways  through  the  j,;, 

11."..  0,  21,  represent  the  plan  and  sectjon  of  a 

gallery  in  two  ti>  ren  in  an  Austrian  work.    The  i 

of  the  gallery  is  closed  by  ■  Bimple  wall,     !■  the  vent- 


.".  I  ELEMENTS   QF    ri:i:M.\M:.NT   WO8K0, 

boles  for  the  escape  of  Binoke,  drains  arc  made  in  the  scarp 
wall,  at  the  li'\*  1  of  the  gallery  door,  to  convey  off  any  water 
that  may  collect  in  it. 

114.. .!':_-.  22,  23,  arc  a  plan  and  section,  from  the  same 
authority,  of  a  gallery  behind  the  lower  portion  of  the  scarp 
wall,  the  upper  portion  being  connected  with  relieving  arches, 
so  arranged  that,  being  open  to  the  rear,  the*  foot  of  the  Blope 
of  earth  will  just  touch  the  back  of  the  wall  at  its  foot  within. 
Jn  this  example,  the  pressure  of  the  earth  being  supposed  to  be 

•.  the   gallery  is  closed   in   the   rear   by   arched    walls;   the 

arches  being  built  into  the  vertical  piers,  Z?,  of  the  relieving 
arches,  ('.  This  example  also  shows  the  manner  of  barricad* 
ing  the  door-ways  through  the  piers  by  vertical  grooves,  made 

in  the  opposite  faces  of  the  piers,  to  receive  the  scantling  ibrin- 
ing  the  barricade. 

115.. .In  Fig.  28  is  shown  the  section  of  a  gallery  behind  the 
lower  portion  of  the  scarp,  with  the  upper  portion  arrange  1 
with  recesses  for  loop-holes. 

llG...C\>r.\T]:i;x  arc  (i.M,i.i:i;ii>.  PI.  -1.  Fig.  35.  The  most 
simple  method  <>!'  arranging  a  gallery  behind  a  counterscarp 
wall,  for  the  defence  of  a  ditch,  is  to  build  another  wall  par- 
allel tu  that  of  the  counterscarp,  and  to  throw  an  arch  over 
between  the  two  to  cover  the  top  of  the  gallery.  The  counter- 
scarp wall  is  pierced  with  loopholes* arranged  in  the  same 
way  as  in  scarp  galleries. 

1  1  7. ..The  example  selected  is  from  one  of  our  works,  and 
shows  a  section  of  the  gallery  through  a  loop-hole.  -1, 
counterscarp  wall;  D,  parallel  wall;  (7,  arch  and  capping;  E, 
glacis  mask  covering  the  scarp  wall. 

lis. ..In  Fig>.  1".),  P>0,31,  are  shown  a  plan,  section  on  r  6, 
and  a  section  and  interior  elevation  on  fljp,  of  a  counterscarp 
gallery  taken  from  a  French  authority.  In  this  case  counter- 
forts, Bquare  in  plan,  are  built  along  the  back  of  the  counter? 
Scarp  wall,  leaving  8  feet  between  them.  Parallel  to  the 
counterscarp  .wall,  and  4  feet  in  rear  of  the  counterforts, 
another  wall   is  built,  which,  with  the  counterforts,  serves  as 


COMTONENT    ELEMENTS   OF    1'KIIM  A  M  AT    WOBK.S.  55 

tlic  support  of  a  scries  of  arches  perpendicular  to  the  counter- 
scarp wall,  sprang  between  tin-  counterforts,  and  another 
parallel  to  it  and  resting  on  the  counterforts  and  parallel  wall. 
The  arches  between  the  counterforts  form,  with  them,  re- 
I,  for  the  men  serving  the  loop-holes,  pierced  in  the 
Counterscarp  wall;  whilst  the  covered  space,  />',  in  rear,  servo 
for  circulation,  without  disturbing  the  men  engaged  in  firing. 

119.. .Counterscarp  galleries  may  also  be  arranged  for  a  ditch 
defence  with  artillery — short  guns,  like  carronades,  being  used 
for  this  purpose.  A  plan,  Fig.  32,  a  vertical  section  and  side 
elevation  on  D  C,  Fig.  88,  and  a  section  and  hack  elevation 
on  A  B,  Fig.  34,  taken  from  one  of  our  works,  shows  a  dis- 
position of  this  kind  in  the  reentering  angle  of  the  counter- 
scarp. 

lL'<i...r,.wiI,,NM  is.  In  small  works,  where  a  flanking  dis- 
position cannot  he  obtained  from  the  enceinte,  as  in  Lunettes 
and  redoubts,  the  ditches  may  he  swept  by  covered  chambers, 
Pi.  5,  Fig.  39,  attached  to  the  scarp  wall  either  at  the  centre 
of  tin-  sides  of  the  work  or  at  the  angles. 

These  chambers,  PI.  5,  Fig.  39,  are  usually  of  a  pentagonal 
form — the  sides  which  join  the  scarp  wall  serving  to  flank  it, 
and  the  two  exterior  sides,  forming  a  salient  angle,  delivering 
their  fire  on  the  opposite  counterscarp  and  it>  crest.  From 
their  form  and  purposes,  they  have  received  the  name  of 
bastionnets. 

The  dimensions  of  these  constructions  will  depend  upon  the 
amount  and  kind  of  lire  to  be  delivered.  Their  scarps  should 
be  as  high  as  that  ot  the  main  work.  They  Communicate  with 
the  interior  of  the  main  work,  either  directly  by  gallery  or 
postern,  or  from  a  scarp  gallery. 

:;:»  show.-  a  plan  of  a  bastionnet,  /A  at  an  angle  com- 
municating with  a  scarp  gallery,  /'.'.  In  rear  of  the  scarp 
gallery,  and  opposite  to  the  bastionnet,  is  placed  a  small 
powder  magazine  for  it.-  service.  The  example  is  from  Aus- 
trian authority,  and  i-  arranged  tor  one  small  gun  on  each 
flank  besides  the  loop-holes  tor  small  arms. 


OOMPONKNI     ELEMKNT8  O]     PKRXAKENT    WORKS. 

121. ..As  il  rule,  it  may  be  laid  down  that  the  Balieiit 

angles  of  the  redoubt  are  the  most  suitable  positions  for  the 
bastionnets,  as  they  will  thus  form  small  bastioned  fronts,  in 
which  both  the  Bides  of  the  main  work  and  those  of  the  bas- 
tionnet  will  be  swept  by  the  flanks  of  the  latter.  The  only 
danger  in  this  arrangement  is,  that  the  loop-holes  in  one  Hank 
may  be  fired  into  from  the  opposite  one.  This,  however,  may 
be  guarded  against  by  a  suitable  position  given  to  the  loop- 
holes. 

L22.. .As  the  main  object  of  covered  defences  is  protection 
against  shells,  it  is  essential  that  the  arches  of  the  galleries 
an.d  bastionnets  should  be  bomb-proof.  As  the  Bpan  of  these 
arches  is  usually  small,  a  thickness  of  2  feet  given  to  the 
masonry,  and  a  covering  from  4  to  6  feet  of  earth  above  it,  is 

ordinarily  considered  sufficient  for  the  object  in  view. 

123. ..With  regard  to  the  front  walls  of  these  constructions, 
as  they  are  too  thin  to  withstand  the  direct  action  of  artillery, 
they  must  either  be  covered  by  earthen  masks,  as  a  glacis 
raised  beyond  the  counterscarp  for  example,  or  he  used  only 
in  positions  where  they  are  not  e.xposedto  this  tire. 

1 J 1. ..It  should  be  observed  that  whatever  advantages  cov- 
ered defences  afford  as  shelter  from  the  assailant's  fire,  they 
present  the  inconveniences  of  a  comparatively  narrow  and  ob- 
structed iield  of  view  to  the  assailed,  which  is  further  obscured 
by  the  smoke,  which  may  gather  within  the  gallery,  and  in 
front  of  the  loop-holes.  From  these  causes  the  assailed  having 
to  aim  at  a  venture,  his  fire  is  likely  to  be  less  effective  than 
in  open  defences  where  the  smoke  disperses  rapidly  and  leaves 
a  (dear  Held  of  view.  The  same  may  be  said  of  loop-holed 
Avails  covering  exterior  corridors  where  the  space  to  the  rear 
is  confined. 

Owing  to  these  considerations,  loop-holed  and  covered  de- 
fences  of  the  kind  in  question  should  be  restricted  to  special 
defensive  purposes,  where  an  object  within  the  held  of  fire 
can  be  attained  with  some  certainty,  whether  seen  or  not  by 
the  assailed;  as,  for   example,  the  protection  of  a  ditch,  or  a 


4 


COMPONKNT   ELEMENTS   OF    PERMANENT    WORK8.  57 

scarp  wall  which  cannot  be  flanked  from  within  the  work  for 
sweeping  a  covered-way,  or  the  interior  of  any  outwork  which 
cannot  be  brought  well  under  the  tire  of  the  parapet  of  the 
main   work. 

125...Caponniekk  Defences  bob  the  EnckinTE  Ditch — 
These  works  are  classed  under  the  head  of  what  are  termed 
defetvsive  casemates,  whick  are  bomb-proof  arched  structures 
for  receiving  cannon,  which  lire  through  embraaurea  pierced 
in  the  front  or  mask  wall  of  the  casemate*  Defences  of  this 
class,  when  used  to  flank  the  main  ditch,  are  usually  termed 
mated  caponnieres. 

1lm>... These  defences  arc  usually  placed  in  the  main  ditch  at 
the  middle  point  of  the  side  or  front  to  he  flanked.  The  out- 
line of  their  plan  is  mostly  that  of  a  lunette,  PI.  5,  Fi^.  36 — 
the  flanks  being  perpendicular  to  the  line  of  the  scarp,  and 
the  two  face.-  making  a  salient  angle  of  60°.  The  caponniere 
is  either  built  in  juxtaposition  with  the  enceinte,  or  else  de- 
tained from  it.  In  the  latter  case,  an  enclosure  is  formed  be- 
tween the  two  by  a  loop-holed  wall  which  connects  the  flanks 
with  the  scarp  wall.  Each  flank  consists  of  one  or  two  tiers  of 
arched  chambers — the  piers  of  the  arches  being  perpendicular 
to  the  hack  of  the  walls  of  the  think.  Each  chamber  is  of 
sufficient  dimensions  for  the  service  of  a  single  gun  with  a  con- 
tracted field  of  fire,  I'].  5,  Figs.  36,  -">7.  In  some  cases,  loop* 
holes  are  pierced  for  small  arms  on  each  side  of  the  embrasure ; 
in  others,  the  casemates  of  one  story  are  pierced  for  cannon  and 
the  other  for  small  arms. 

127. ..The  <•..  are  closed  in  rear  by  a  thin  wall,  which 

is  provided  with  windows  for  light   and    ventilation;  and   the 
piers  are  pierced  with  door-wavs,  to  form  a  communication 
between  the  chambers  and  to  assist  the  ventilation.     Elm  - 
venfa,  Fig.  37,  are  made  in  the   front   wall,  just   under  the 
arches,  for  a  like  purp — .     Wnere  it  may  be  necessary,  the 

lower  floor  is  drained  by  a  Conduit  through  tlw  front  wall. 

l-v....\  lefl   between  the  d  each 

flank  rered  at   top  with  from  4  to  6  feel   of  earth,    The 


KPONZNT    !  l.l  MINT.-  OF   Ti:i;M.\Nl'NT   WORKS. 

flani  parated  from  the  faces  by  a  closed  corridor,  which 

communication. 

1  •_".'. ..In  front  of  the  corridor  and  on  each  side  of  the  axis  of 
the  caponni6re,  a  easemated  chamber,  which  is  open  in  front, 
ia  arranged  for  one  mortar,  Pigs.  .'!»'>.  -'Is.  The  arches  of  these 
ehambers  rise  toward  the  front,  the  better  to  subserve  the  ob- 
ject in  view. 

130. ..On  one  side  of  the  chambers  the  powder  magazine  is 
placed,  with  a  store-room.     On  the   other  side  a  stair-way  be- 
:i  the  stories  is  built. 

131. ..The  space  within  the  salient  angle,  enclosed  by  the 
walls  of  the  faces  and  the  front  of  the  mortar  casemates,  is 
open  at  to] >.  It  has  an  open  corridor  for  communication,  and 
the  front  walls  are  arranged  with  loop-holed  recesses  for  small 
arms,  Figs.  36,  38. 

132. ..The  enceinte,  in  rear  of  the  flanks  of  the  caponniere,  is 
arranged  with  a  scarp  gallery,  to  flank  the  caponniere  flanks 
and  the  court  between  them.  A  break  is,  in  some  cases,  made 
in  the  line  of  the  scarp  wall,  pWpendicular  to  the  caponniere 
laces,  and  casemates  for  cannon  and  small  arms  arranged  be- 
hind the  scarp  wall  to  flank  these  faces.  In  some  cases  these 
flanking  dispositions  are  placed  in  front  of  the  scarp  wall,  the 
casemates  being  open  to  the  rear,  looking  on  a  narrow  court 
between  them  and  the  scarp  which  is  closed  on  the  sides  by  a 
loop-holed  wall. 

133. ..The  example  here  given  of  a  casemated  caponniere  is 
from  an  Austrian  authority.  Fig.  36  is  the  plan;  Fig.  37  a 
section  and  elevation  on  A  £  of  one  flank  and  the  end  wall  of 
the  corridor  looking  toward  the  court  between  the  flanks ;  Fig. 
38  a  section  and  elevation  along  0'  D'  of  the  corridor,  mortar 
casemate  and  triangular  court ;  Figs.  37,  38,  are  on  an  en- 
larged scale. 

134... Casemates  on  Land  Fronts.  Various  modes  have, 
from  time  to  time,  been  proposed  for  arranging  defensive  case- 
mates lor  the  exterior  defence  on  land  fronts.  The  difficulty 
in  covering  the  masonry  from  the  batteries  of  the  assailant  has 


niMi'iiNKXT    ELEMENTS  OF    PERMANENT    WORKS.  59 

been  the  chief  objection  to  these  structures,  and  is  the  more 
prominent  as  the  fire  of  artillery  becomes  more  accurate,  as 
such  casemates  would  soon  be  ruined  or  rendered  untenable 
bjT  embrasure  shots. 

135. ..The  structure  for  this  purpose  which  has  been  most 
applied  within  late  years,  is  what  is  termed  the  Haxo  casemate  / 
the  details  having  been  first  proposed  by  General  Haxo,  one 
of  the  first  authorities  of  the  French  school  of  engineers. 
These  casemates  consist,  Figs.  45,  46,  47,  of  a  series  of  arched 
bomb-proof  chambers;  dosed  in  front  by  a  thin  mask  wall, 
which^exeept  around  the  embrasures  through  it,  is  covered 
from  Wk  assailant's  artillery  by  the  parapet.  To  present  but 
a  small  surface  of  masonry  to  fire,  the  arches,  which  are  hori- 
zontal and  perpendicular  to  the  mask  wall  for  the  greater 
portion  of  their  length,  descend  toward  the  front,  leaving, 
where  they  join  the  mask  wall,  just  sufficient  height  within  for 
the  service  of  the  gun.  To  effect  this,  the  anterior  portion  of 
the  arch  must  be  conoidal  in  shape, 

13G...The  piers  of  the  arches  are  pierced  with  wide  arched 
openings,  which  serve  the  double  purpose  of  a  communication 
between  the  casemates  and  to  give  the  gun  a  wider  traverse 
for  firing. 

137... Embrasures  are  pierced  in  the  parapet  in  prolongation 
of  those  of  the  mask  wall,  and  it  is  proposed  to  cover  the 
small  portion  of  the  masonry  necessarily  exposed  by  this  ar- 
rangement, by  placing  several  thicknesses  of  heavy  timber  in 
front  of  it  to  receive  the  shot. 

138. ..When  the  casemates  serve  simply  for  the  cover  .of  the 

cannon,  the  arches  are  covered  with  (torn  4  to  6  feel  thickness 

of  earth,  and  are   left  open   to   the  rear  for  rlie   more  prompt 

]><■   of  the   smoke,  and   ■  ditch   is  sometimes   made  jusl  in 

^rear  of  the  casemate*  to  ditch  bombs  ami  limit  the  effects  of 
their  explosion.  When  the  arches  are  made  longer  than  for 
the  service  of  the  guns  alone,  the  earthen  covering  is  sometimes 
arranged  with  a  parapet  to  cover  cannon  in  barbette,  or  for 


■     •- 


IfPONBHT  -   CW   !'I:i:ma.mnt    WORKS. 

l39...The  examples  shown  by*' the  figures  is  from  a  French 
authority.     Fig.  45  is  a  plan  od  m  n,  Fig.  17  :  Fig.  46  a  - 
tion  and  interior  elevation  toward  the  mask  wall  on  o  y,  Fig. 
47:  and    Fig.   17  a  section  ami  Bide  elevation  on  /•  *,  Figs. 
45,  46. 

14".. .In  Figs.  48,  1!',  is  shows  an  arrangement  of  two  case- 
mates of  the  Haxo  kind,  from  an  Austrian  authority.  In  this 
case,  tin1  masonry  is  covered  on  the  flanks  from  enfilading  fire 
1>\  earth.  Fig.  48  is  an  interior  elevation  of  the  arches,  and 
the  hack  wall  that  retains  tile  earth  on  the  sides.  Fig.  49  is  a 
Longitudinal  section,  and  shows  the  maimer  of  cove^ng  the 
masonry  in  front  and  securing  the  earthen  embrasiPb  by  a 
timber  facing. 

141...MobtaE  C askmatks.  In  Fig.  50,  PI.  6,  is  shown  a 
longitudinal  section  of  a  mortar  casemate  placed  in  rear  of 
a  parapet,  by  which  it  is  covered  from  direct  fire.  The  arch 
is  covered,  as  in  the  preceding  case,  by  earth,  to  break  the 
shock  of  shells.  It  rises  toward  the  front,  to  give  ample  room 
for  the  shell  in  its  flight.  The  casemates  are  covered  on  their 
flanks  from  enfilading  fire  by  an  embankment,  and  are  partly 
closed  by  a  wall  in  rear.  A  small  ditch  is  made  in  front  of 
the  chamber,  and  a  slight  wall  built  within  it,  to  give  cover 
from  the  splinters  of  shells  falling  between  the  parapet  and 
casemate1.  Arched  chambers  are,  in  some  cases,  made  beneath 
the  mortar  chamber,  which  serve  as  store-rooms  and  temporary 
magazines. 

142. ..When  these  casemates  are  placed  in  rear  of  a  portion 
of  the  parapet,  but  little  exposed  to  direct  fire,  the  thickness 
of  tlie  parapet  in  front  of  them  may  be  reduced,  and  the  in- 
terior slope  lie  replaced  by  a  breast-height  wall  along  the  front 
of  the  casemates,  in  order  to  give  better  cover  in  flank  and 
from  slanl  lire,  by  throwing  forward  the  casemates  more  undent 
cover  of  tin'  parapet. 

1  l3...The  example  given  is  from  the  same  authority  as  in 
the  preceding  example  of  casemated  caponnieres. 

I  1  L. Casemates  foe  Water  Fronts.     In  the  casemated  bat- 


M 


COMPONENT    ELEMENTS  OF    l'KUMA.NKNT    WORKS.  61 

terics  for  sea-coast  and  harbor  defence,  the  scarp  or  mask  wall 
of  the  chambers  for  the  guns,  being  exposed  to  the  iire  of 
ships  alone,  are  not  covered^  as  on  land  fronts,  by  an  earthen 
mask  j  these  walls  being  built  of  sufficient  thickness  and 
strength  to  withstand  the  lire  of  the  heaviest  guns  within  the 
range  that  .ships  can  venture  1<>  attack,  and  being  far  less  vul- 
nerable than  the  wooden  or  iron  sides  of  vessels  thus  far 
brought  into  general  use. 

145. ..These  batteries,  in  our  own  and  European  works,  con- 
sist of  a  series  of  arched  bomb-proof  chandlers,  which  serve 
for  the  service  of  the  guns  alone;  or  else  the}'  receive  such 
dimensions  that  the  portions  <>t'  the  chambers  immediately  in 
rear  of  the  mask  wall  arc  appropriated  to  the  service  of  the 
batten,  and  the  rear  portions  are  converted  into  quarters, 
store-rooms,  and  other  necessary  purposes  for  the  garrison. 

1  Hi. ..In  the  earlier  sea-coast  casemated  defences  constructed 
in  onr  Bervice,  the  gun  chambers  have  received  dimensions  to 
admit  of  two  guns  in  each  chamber,  PL  5,  Figs.  4<>,  41.  The 
chambers  are  usually  formed  of  segmental  brick  arches  of 
L20°,  which  rest  upon  6tone  piers  built  back  perpendicular  to 
the  mask  wall.  In  the  example  given,  the  arches,  C,  have  a 
uniform  thickness  of  3  feet,  exclusive  of  the  roof-shaped  cap- 
ping, which  i>  generally  of  rubble  and  betoii.  and  which  is 
red  on  top  by  the  earth  «»f  the  parapet  ami  rampart.    The 

/»'.  are  frf    f.-ct  thick,  and  are   pierced  with  arched 

communications,   /•".  a  few  feet  in  rear  of  the  mask  wall, 
placed  as  to  give  the  gun-carriage  a  wider  traverse  by  allowing 
it  to  run  under  this  opening.     Arched  recesses,  /.'.are  made  in 
the  mask  wall  t.»  admit  the  muzzle  of  the  gun  being  well  run 
out.  bo  a.-  to  clear  the  casemate  <>t'  smoke.     An  embrasur 
i>  pierced  at  the  centre  of  each  receBS,  the  sole  being  at  the 
proper  height  above  iil(.  floor  of  the  casemate,  to  accommod 
the  casemate  chassis  and  top  carriage.     In  Pig.  40,  i.-  shown 
the  plan  and  dim  >f  the  embrasures  usually  adopted  in 

onr  works,  until  .  and  in  Fig.  J],  whid 

n  vertical  section  of  tin  casemate  through  the  axis  of  an  em 


«.*■ 


62  OOMPONENl    ELEMENTS  OF    riKMAM.vr    WOBES. 

lira-ure.  is  shown  tin'  elevation  and  dimensions  of  the  cheeks; 
,,  of  the  embrasure.  In  the  casemates  of  Borne  of  owr  works, 
flues  for  ventilation  and  carrying  off  rapidly  the  powder  smoke, 
run  from  t}ie  top  of  the  carriage  recesses,  /.',  through  the  ma- 
sonry of  the  scarp  wall,  and  have  their  outlet  in  the  top  of  the 
wall.  In  others,  the  fines  run  from  the  casemate  arch  to  the 
top  of  the  parapet.  Peneath  the  embrasure  a  recess,  termed 
the  tongtte-hole^  which  in  plan  is  triangular,  is  made  to  receive 
the  tongue  of  the  chassis.  The  tongue  is  confined  in  it&place, 
and  the  chassis  traverses  around  a  pintle  which  is  received  into 
the  pintle-hole,  made  at  the  centre  point  of  the  throat  of  the 
embrasure,  ami  extending  into  the  masonry  below  the  tongue* 
hole. 

147. ..When  the  casemates  serve  also  as  quarters  for  the  gar- 
rison, the  rear,  toward  the  parade,  is  closed  by  a  brick  or  stone 
parade  wall,  which  forms  the  front  wall  of  the  quarters.  A 
brick  partition  wall  separates  the  quarters  from  the  gun  gal- 
lery. Arched  recesses  and  flues  are  made  in  the  piers  for 
chimneys  ;  and  the  parade  wall,  the  sides  of  the  piers,  and  sof- 
fit  of  the  arch,  are  suitably  finished  to  give  a  dry  and  well 
ventilated  dwelling. 

148.. .In  the  example  here  given,  as  in  most  of  our  earlier 
casemated  works,  there  is  but  one  tier  of  casemated  guns  ;  this 
tier  being  surmounted  by  a  barbette  battery,  covered  either  Ivy 
an  earthen  or  stone  parapet  on  the  water  fronts. 

1  !'.»... Casemates  adapted  to  two  guns  in  each  room,  present 
a  more  vulnerable  mark  in  the  portion  of  the  mask  wall  be- 
tween the  piers  ;  expose  more  men  to  danger  from  embrasure 
shot>  :  present  a  greater  opening,  in  rear,  to  the  assailant's  fire, 
when  not  closed  by  a  parade  wall ;  offer  less  resistance  to  the 
shock  of  shells,  and  are  more  difficult  to  construct,  without 
settling,  than  rooms  for  single  guns.  These  advantages  in 
favor  of  casemates  for  single  gnns  are  the  more  marked  where, 
tor  the  purpose  of  obtaining  a  heavy  fire  in  some  fixed  direc- 
tion, it  is  desirable  to  resort  to  a  castellated  structure,  consist- 
ing of  several  tiers  of  casemates. 


COMPONENT    ELEMENTS  OF.  PEBMANENT   WORKS.  C>3 

150.. .In  PL  6,  Figs.  42,  b),  4  t,  is  shown  ft  plan.  Fig.  42,  on 
E F,  of  the  first  tier  of  casemates;  a  vertical  section  and  side 
elevation,  Fig.  43,  on  A  B,  of  the  three  tiers  of  casemates  and 
the  top  barbette  battery  ;  and,  in  Fig.  41,  an  interior  elevation 
on  CD,  of  one  of  the  most  recent  of  these  structures  for  the 
defence  of  the  channel  leading  to  one  of  onr  harbors.  Besides 
the  wide  arched  openings  F.  through  the  piers,  for  communi- 
cation and  the  traverse  of  the  guns,  smaller  door-ways,  a,  arc 
made  for  communications  in  rear  of  the  battery.  The  case- 
mates are  Open  in  the  rear.  The  arches  of  the  top  tier  are 
alone  made  bomb-proof;  those  of  the  lower  tiers  receiving  suf- 
ficient strength  to  receive  the  armament  and  admit  of  the  ser- 
vice of  the  guns  with  safety. 

15L.J£mBbaSUBES.  The  form,  dimensions  and  construction 
of  embrasures  in  mask  walls,  present  a  problem  which  has  of- 
fered no  little  difficulty,  in  a  satisfactory  solution,  toengim 
by  which  the  best  coVer  could  be  given  to  the  guns  and  men, 
by  exposing  the  least  surface  to  embrasure  shots,  whilst  the 
guns  should  receive  a  suitable  traverse  to  command  a  wide 
field  of  fire. 

152. ..In  the  embrasures  of  our  works  the  general  form  is  the 
same  as  those  usually  found  in  Europe,  but  they  present  a  very 
considerable  less  amount  of  exterior  and  throat-opening  than 
European  embrasures.  See  PL  7.  Fig.  59,  which  is  the  plan 
of  a  French  carriage  recess  and  embrasure  for  a  Bingle  gun. 
and  Fig.  ''-'I,  which  is  one  of  the  same  parts  of  an  English  fori 
for  sea-coast  defence.  In  some  of  onr  earlier  works,  the  sole, 
cheeks  and  top  of  the  embrasures  are  constructed  of  brick,  as 
being  a  material  thai  would  be  less  destructive  through  the 
splinters  driven  in  by  embrasure  shots.  This  view,  however, 
has  been  abandoned  in  our  more  recent  works,  the  embrasures 
being  constructed,  on  the  contrary,  of  heavy  stone  blocks, 
cart fully  and  Strongly  bunded;  a  brick  arch  being  thrown 
above  the  embrasure,  within  the  mass  of  the  mask  wall,  to 
secure  the  upper  portion  from  yielding  should  the  block  form- 
ing the  ceiling  of  the  embrasure  be  damaged. 


64  ELEMENTS  "''   r:  kmanknt   WOBXB. 

153...A  further  and  most  important  step  lias  been  more  re- 
tlj  taken,  in  the  application  to  embrasures  of  wrOnght-iron 
and  throat-pieces,  with  shutters  <>i"  the  same   mar, 'rial, 
linst  heavy  ahol  and  grape.     The  first  applied 
■  it'  this  means  has  been  made  to  the  embrasures  of  on 
works  now  in  the  course  of  "Construction ;  and   the  forms, 
dimensions  and  construction  of  the  embrasures  are  the  results 
of  experiments  carefully  made  with  the  heaviest  solid  shot  and 
-rape,  upon  walls  and  embrasures  of  various  forms  and  dimen- 
sions, under  the  directions  of  General  Totten,  chief  engineer- 

1.".  I. ..The  form  adopted  is  shown  in  plan  in  IM.  S,  Kin-,  ill  — 
tin-  interior  portion  being  trapezoidal,  and  the  exterior,  beyond 
the  throat,  rectangular.  This  form  was  adopted  with  the 
double  view  of  limiting  the  effects  of  embrasure  shot,  which, 
in  the  old  forms,  striking  the  oblique  surfaces  of  the  cheeks  of 
the  exterior  portion  and.  glancing  inward,  occasioned  consider- 
able casualties,  and  to  form  a  suitable  recess  for  strong  iron 
shutters  to  protect  from  grape  entering  through  the  throat 
whilst  the  gun  was  out  of  battery.  The  tw6**principal  wrought- 
iron  throat-pieces  are  trapezoidal  in  plan,  being  8  inches  thick 
and  17  inches  base,  the  oblique  side  having  the  same  slant  as 
the  inner  cheek  of  the  embrasure.  Exterior  to  these  two 
pieces  are  two  plate-pieces,  each  two  inches  thick,  against 
which  the  shutters,  which  are  also  two  inches  thick,  rest  when 
open  or  closed,  as  shown  in  Fig.  01.  There  is  also  a  wrought- 
iron  plate  casing  around  the  exterior  opening  of  the  embrasure, 
as  shown  in  Fig.  61,  and  in  the  exterior  elevation.  Fig*  (!4. 
In  Fig.  G2  is  shown  an  interior  elevation  of  the  carriage  recess, 
the  embrasure,  and  the  tongue-hole  ;  and,  in  Fig.  (!3,  a  verti- 
cal section  and  siiK'  elevation  on  A  B,  Fig.  64,  of  the  embra- 
sure, carriage  recess,  and  the  pintle  and  tongue-holes. 

155... The  exterior  width  of  the  embrasure,  the  obliquity 
given  to  the  cheek.-  of  the  interior  portion,  and  the  depth  and 
slant  given  to  the  carriage  recess  and  its  sides,  are  arranged 
with  a  view  to  the  traverse  of  the  gun,  which  is  fixed  at  o'0°, 
or  3<>°  on  each  side  of  the  axis  of  the  embrasure. 


COMl'o.NKNT    ELEMENTS  OF   PERMANKNT    WORKS.  05 

156. ..All  the  parts  of  the  wall  adjacent  to  the  embrasure  are 
constructed  of  the  largest  sized  blocks  of  the  toughest  stone, 
the  blocks  being  carefully  fitted  and  bonded,  and  having  the 
additional  strength  afforded  by  a  very  ingenious  arrangement 
of  hollow  bolts,  and  a  concrete  of  lead  and  ehippings  of  stone 
run  together.  A  brick  arch,  as  shown  in  the  elevations  and 
sections,  is  turned  over  the  embrasure  and  within  the  mass  of 
the  scarp  wall. 

157...Bomi;-j>roof  Bnr.mxos.  Casemated  bomb-proof  quar- 
ters are  indispensable  to  the  safety  and  comfort  ofthe  garrison 
during  siege  or  any  prolonged  attack  for  the  annoyance  or  re- 
duction ofthe  work  by  a  bombardment.  In  small  works  like 
the  most  of  our  forts,  which  are  chiefly  designed  for  sea-coast 
defence,  casemated  quarters  are  arranged  as  has  been  seen  in 
the  rear  of  the  batteries,  a  portion  of  each  casemate  toward 
the  parade  being  partitioned  off  and  suitably  disposed  for  the 
object  in  view.  In  some  cases  advantage  is  taken  of  a  scarp 
wall,  on  a  land  front,  which  is  well  covered  by  a  glacis  or 
other  face  cover,  to  form  in  its  rear  quarters  of  this  character. 
In  all  cases,  care  should  be  taken  to  place  such  quarters  on 
those  fronts  which  are  best  covered  from  a  direct  fire,  and  the 
parade  walls  of  which  are  not  exposed  to  reverse  fire.  When- 
ever the  plan  of  the  work  admits  of  it,  quarters  of  this  kind 
should  he  arranged  for  defence,  by  being  pierced  with  loop- 
hole.-, and  even  with  embrasures  for  cannon.  Defensive  case- 
mated  quarters  form  a  prominent  and  distinctive  feature  in 
what  is  now  known  as  the  German  school  of  permanent  fortifi- 
cation. They  consist  of  bomb-proof  buildings  of  a  curvilinear 
or  polygonal  plan,  arranged  for  one  or  more  Btories  of  covered 
defences,  with  an  ordinary  open  defence  surmounting  tin- 
ca>emates.  The  casemates  of  the  upper  story  are  covered  by 
bomleproof  arches,  whilst  those  of  the  lower  Btories  re© 
flal  segment  arches  of  only  sufficient  thickness  and  strength  to 

bear  the  Weight  of  the  guna  and  to   subserve  the   other  ol.j. 

of  the  structure.     When  employed  a.-  caponnien 
defences,  or  as  interior  retrenchments,  the  front  walls  of  ti. 


IIIMI  Ni-   OF    PERMANENT    WOKS. 

structures  are  masked  from  direct  views,  either  by  the  glacis 
or  by  the  parapel  of  the  work  in  which  they  are  placed,  and 
they  receive  a  thickness  of  at  least  5  feet.  But  as  a  mask 
Avail  even  of  this  thickness,  When  pierced  with  loop-holes  and 
embrasures,  is  liable  to  damage  from  shot  which  plunge  over 
the  parapet  in  front  <>i'  it.  PI  7.  Fig.  53,  the  portions  of  the 
mate  piers,  //,  where  they  j< »in  the  mask  wall,  -1.  are 
made  thicker,  in  some  cases  for  a  distance  of  a  few  feet  hack, 
than  their  general  thickness,!in  order  to  receive  two  vertical 
grooves  in  the  face  of  this  thicker  portion,  into  which  scantling 
being  inserted  horizontally,  and  the  Bpace  between  the  two 
partitions  thufl  formed  filled  in  with  sand-bags  or  other  shot- 
proof  materials,  a  temporary  shelter  can  be  formed  when  the 
rnin  of  the  mask  wall  exposes  the  interior  of  the  casemate  to 
view. 

In  our  service,  PI.  7,  Figs.  51,  52,  when  casemated  quarters 
are  constructed  of  two  stories,  the  upper  one  alone  is  covered 
with  a  bomb-proof  arch,  the  floor  between  the  two  being  of 
timber,  ami  constructed  in  the  ordinary  way. 

158.. .In  Fig.  51  is  shown  a  plan  on  A  D,  Fig.  52,  of  bomb.- 
proof  casemated  quarters  in  rear  of  a  scarp  wall  and  of  a 
counterscarp  gallery,  both  arranged  with  loop-holed  defences. 
Fig.  52  is  a  section  and  side  elevation  on  CD,  Fig.  51,  show- 
ing the  rampart  and  parapet  over  the  arch  and  tin1  fireplaces 
and  chimneys  in  the  piers  of  the  arches.  The  floor  of  the 
second  story  is  of  timber.  The  rear  or  parade  wall  is  pierced 
with  doors  and  windows. 

ir.it...  In  Fig.  ;,:;  is  shown  the  plan  of  the  end  of  a  casemated 
defensive  barrack,  from  an  Austrian  authority.  The  front 
wall,  J,  is  arranged  and  pierced  for  cannon,  each  arched 
chaniher  for  one  gun.  The  end  wall  is  loop-holed  for  mus- 
ketry, and  the  rear  wall,  ( \  has  windows  and  doors. 

160...PowDfBB   Magazine.     The  structures  for   this  purpose 

built  with  strong,  full   centre,  bomb-proof  brick   arches, 

supported  on  heavy  .-tone  piers,  which  form  the  outward  walls 

and   to  which   interior  buttresses  are  sometimes  added.     The 


COMPOXKN  I    ELEMENTS  OF    HKMAMM     WORKS.  67 

capping  of  the  arches  is  covered  with  from  4  to  G  feet  of 
solidly  packed  earth.  The  interior  of  the  magazine,  the  Hours, 
and  the  doors  and  windows,  are  built  with  a  view  to  security 
from  fire;  and  to  preserve  the  pow4er  from  dampness,  by  a 
good  system  of  drainage  around  the  foundations,  and  of  ven- 
tilation by  means  of  air-holes  made  through  the  piers,  and 
panels  of  copper  pierced  with  smal]  holes  placed  in  the  doors. 
No  iron  or  steel  fastening  or  sheeting  is  allowed  in  any  part  of 
the  atrdature;  and  in  arranging  the  air-holes  through  the 
piers,  they  receive  a  broken  direction  ami  have  ;i  copper  mesh- 
work  placed  across  them,  to  prevent  any  combustible  material, 
or  rats,  or  mice,  penetrating  to  the  interior  of  the  magazine. 

In  large  works  the  magazines  are  isolated,  as  far  as  practica- 
ble, from  the  enceinte,  so  aa  not  to  endanger  it  should  an  acci- 
dental explosion  take  place.  The  magazine  is  enclosed  by  a 
strong  high  wall  for  security,  and  is  provided  with  lightning 
rods.  In  small  works  some  one  or  more  of  the  casemates,  in 
the  least  exposed  position  to  the  assailants  lire,  is  built  for  the 
pur] loses  of  a  magazine. 

COMMTXICATIONS. 

I61...The  communications  form  a  very  important  element  in 
the  defence  of  permanent  works.  They  consist  of  r<im]>sy 
stairs.  i.-ir.njs  and  bridges. 

162...Ramp8.  Ramps  are  inclined  planed,  or  path.-,  leading 
from  one  level  to  another,  aa  from  that  of  the  parade  to  the 

plein  of  the  enceinte.     Their  width  at  top,  for  thi 
of  the  artillery  and  other  vehicle.-,  may   he  from  10  to  15 
and   their  inclination   from    L-6   to    1-15,  or   less,  depending  00 
the  difference  of   level   to  he  overcome.     They  are  usually 
placed   in  positions  where  they  will  occupy  the  least  room  of 
the  j  ilong  the  rampart-slope  of  the  enceinte.     A-  a 

ral    rule,  th<  earth  ;  but    wh< 

■  m  on  the  parade,  ti 
replaced  on  one  or  botl  .  wall   which  the 


Pi  KMANKNT    WOT 

th  of  the  ramp.    When  rani]'-  serve  for  infantry  alone,  thoir 

width  may  be  reduced  to  6  feet,  and  in  some  cases  to  4-  feet. 

L68...Stajbs>     Stairs,  except    for   temporary  purposes,  are 

structed  of  atone;  efcch  step  being  a  Bolid  block  which  is 

t   Long  in  the  clear:  its  breadth  at  top  or  the  tread   li' 

inches,  and  its  height  or  rise  s  inches.     Stair.-  are  nsnalfy 

along  the  counterscarp  and  gorge  walls  of  the  outworks, 

forming  a  < imunication.  for  infantry  only,  between  the  ditch 

and  the  terreplein  of  the  work  to  which  they  lead.  They  are 
used  within  the  enceinte  in  positions  where  there  is  not 
sufficient  room  for  ramps;  or  where;  for  greater  security  from 
surprise,  it  is  desirable  to  present  a  narrower  and  more  difficult 
defile  to  the  assailant.  In  cases  where  room  is  wanting  and 
the  communication  not  in  habitual  use,  the  width  of  the  stair- 
way may  be  reduced  to  4  feet. 

164...Po8TERNB.  Posterns  are  arched  passage-ways  con- 
structed under  the  terrepleins  and  ramparts,  forming  subterra- 
nean communications  between  the  parade  and  the  enceinte 
ditch,  or  between  the  ditches  and  the  interior  of  the  outworks. 
The  width  and  height  of  the  interior  of  posterns  depend  upon 
the  use  to  which  the  communication  is  to  be  applied.  For 
artillery,  the  width  is  usually  taken  at  LO  feet,  and  the  height 
under  the  crown  or  key  of  the  arch  at  least  s  feet.  Posterns 
for  infantry  may  be  only  from  8  to  4  feet  wide,  and  from  6 
feel  6  inches  to  8  feet  high  under  the  crown  of  the  arch.     The 

thickness  of  the  piers  of  the  arches  is  generally  taken  at  about 
half  the  width  of  the  postern.  The  arches  are  from  18  inches 
to  2  feet  thick.  As  any  injury  to  the  arch  from  the  bursting 
of  a  shell  over  it  might  obstruct  the  communication,  the  arch 
should  he  Covered  with  a  thickness  of  at  least  )!  feet  of  earth, 
and.  when  convenient,  with  o  or  6  feet  for  greater  security. 
A  Btrong  wooden  door  i^  placed  at  each  outlet  <»f  the  postern 
to  secure  it  against  surprise.  The  door-way  in  posterns  for  the 
of  artillery  should  he  of  just  sufficient  height  for  the 
convenient  passage  of  a  gun — about  7  feet  for  each  dimension 
IB  usually  allowed  for  this  purp 


OOMPONENT    KT.KMKNTS    OF    I'KUMAM'.XT    WORKS.  fi9 

165. ..The  most  important  postern  is  the  one.  leading  from 
the  parade  to  the  enceinte  ditch.  This  generally  recen 
width  of  12  feet,  and  the  same  height  under  the  crown.  For 
{greater  security  from  surprise,  its  outlet  at  the  enceinte  ditch 
is  at  least  6  feet  above  the  bottom  of  the  ditch — this  difference 
of  level  being  overcome  by  means  of  a  temporary  wooden 
rani]),  which  receives  an  inclination  of  at  least  1-6.  With  a 
like  object,  besides  two  strong  doors  at  the  two  ends  of  the 
postern,  there  is  a  partition  of  masonry  ahout  midway  between 
the  two  ends,  which  is  pierced  with  a  door-way  of  the  same 
size  as  the  door-ways  Df  the  ends,  and  closed  by  a  strong  door, 
which,  as  well  as  Hie  partition  wall,  is  loop-holed  for  musketry. 

166.. .In  cases  where  the  postern  forms  the  main  entrance  to 
the  work,  an  arched  chamber  is  placed  on  one  side  of  it,  at  the 
outlet,  which  serve!  a- 1  guard-room  for  a  few  men,  to  secure 
the  outlet  from  surprise.  The  wall  between  this  chamber  and 
the  postern  is  loop-holed,  so  that  a  fire  can  be  brought  to  bear 
on  the  door-way  of  the  postern  :  and.  as  a  farther  precaution 
against  surprise,  a  machicoulis  defence  is  sometimes  arrai 
at  the  lop  Of  the  scarp  wall  just  above  the  door-way  of  the  pos- 
tern. 

1»;7...(,  mi-way.  In  works  with  large  garrisons,  where  the 
means  of  frequent  communication  with  the  exterior  are  requi- 
site, posterns  of  the  ordinary  dimensions  are  found  not  to  afford 

ifficient  convenience  for  the  daily  wants.      In   such  c:i - 
way  of  sufficient  width  to  admit  of  at  least  a  single 
carriage  road,  with  narrow  foot-paths  on  each  side,  has  to  l>e 

ned  through  the  rampart,  which,  whenever  it  is  practicable 
to  d  iild  be  niched,  and  covered  with  earth  to  ren< 

bomb-]. roof.    This  passage-way  shoul  1.  fi  ity,  have  the 

bottom  of  it-  outlet  at   least  12  feet  above  the  b 
enceinte  ditch  ;  and    when   this  difference  of  level   cannot   be 
obtained,  the  main   ditch  should  be  deepened   sufficiently  for 
Ike  purpose  below  the  outlet.     A  sufficient  height 

and  width  for  the  pa  the  ordinary  \ ,  hiclea  for  th< 

vice  of  the  .  is  mad* 


OOMPOXEHT   ELEMENTS  OF   PEBMAXENT   WOfl 

gate-Way  is  arched  at  top,  where  a  machicoulis  defence  may 
also  be  arranged  to  guard  the  outlel  on  tiw  exterior. 

L68...The  communication  across  the  enceinte  ditch,  Leading 
from  the  gate-way,  is  usually  an  ordinary  wooden  bridge  built 
on  piles.  The  bay  of  this  bridge  at  the  gate-way  is  spanned 
by  a  drawbridge  of  timber,  which  when  drawn  up,  closes  and 
secures  the  gate-way.  This  drawbridge  is  manoeuvred  by  some 
of  the  usual  mechanisms  employed  for  this  purpose. 

L69„.Pobtoulli8.  When  the  gate-way  is  not  preceded  by  a 
ditch,  and  is,  therefore,  without  a  drawbridge,  a  barrier,  termed 
a  j'oilcnUix,  which  can  be  lowered  or  raised  vertically  by 
machinery,  is  sometimes  added  to  secure  the  passage-way  from 
surprise*  The  ancient  portcullis  was  a  framework  of  heavy 
beams,  placed  vertically,  leaving  a  few  inches  only  between 
each  pair  of  beams.  These  vertical  beams  were  either  solidly 
confined  between  horizontal  beams,  or  clamping-pieces  in 
pairs;  <>r  else  they  were  so  arranged  that  they  could  slide  up- 
ward between  the  clamping-pieces.  Each  of  the  vertical 
beams  was  shod  at  the  bottom  with  a  strong  pointed  iron 
shoe.  The  horizontal  pieces  were  framed  securely  with  two 
heavy  vertical  beams  that  formed  the  sides  of  the  frame,  and 
were  fitted  into  vertical  grooves  made  in  the  side  walls  of  the 
passage-way,  in  which  the  frame  could  slide  when  raised  or 
lowered.  By  arranging  the  vertical  beams  to  slide  upward 
between  the  clamping-pieces,  it  will  enable  the  pa.-suge-way 
to  be  closed  in  places  where  an  obstruction  might  be  design- 
edly placed  below  the  portcullis  to  prevent  this  being  done; 
;is  the  beams  which  meet  the  obstruction  would  be  pushed 
upward,  whilst  the  others  would  fall  to  their  ordinary  level 
and  close  the  passage-way  on  each  side  of  the  obstruction. 

1  "<»... In  the  works  recently  constructed  with  us,  the  portcul- 
lis, and  even  tlie  doors  preceding  them,  have  been  constructed 
of  a  strong  open  lattice-work  of  wrought  iron  bars  bolted 
Btrongly  to  the  wrought-iron  uprights  and  cross  pieces  forming 
the  framework  of  the  lattice.  This  is  a  great  improvement  for 
these  purposes,  both  as  to  durability  and  defence. 


ELEMENTS  OV  THE   ri.AX   of    i:ncki.\tf.s    and  OUTWOEK8.      71 

171... Passfi^c-wnys  of  tin's  description  should  be  secured  by 
all  the  means  at  an  engineer  s  disposal.     A  largei  guard-room, 

with  loop-holes  bearing  on  the  passage,  should  he  erected  on 
one  side,  near  the  gate-way  ;  and  if  the  enceinte  is  a  simple 
one,  without  outworks  beyond  its  ditch,  a  small  lunette,  or  a 
loop-holed  tambour  of  masonry  or  timber,  should  he  con- 
Btrncted  beyond  tin-  counterscarp,  forming  a  tele~de~pont,  for 
the  security  of  the  bridge  from  surprise. 

1  7l\. .The  drawbridge,  which  for  convenience  of  manoeuvring 
should  not  be  longer  than  12  feet,  is  constructed  in  the  usual 
mode.  Care  should  be  taken  that  it  shall  fit  the  recess  in  the 
face  of  the  wall  so  closely  that  there  will  not  he  room  enough 
between  it  and  the  jambs  of  the  gate-way  to  insert  an  iron 
lever  to  force  back  the  bridge. 


ELEMMS  OF  THE  PLAX  OF  EXCE1MES  AXD  OUTWORKS. 


KM  KINTKS. 

17". ..The  most  simple  mode  of  fortifying  a  position  in  a  per- 
manent manner.  in  enclosing  it  with  a  rampart, 
mounted  by  a  parapet  with  a  ditch,  the  Scarp   of  which,  when 

dry,  ia  revetted  with  masonry,  and  bo  covered  by  an  earthen 
b  that  it  cannot  lie  breached  except  by  batteries  placed  on 
the  bord<  r  <>f  the  counterscarp. 

174... An  enclosed  tine  of  fortification  of  thig  simple  charac- 
ter is  termed  the  /„„///  <■/ 


rl       BLEMENT8    OF   THE    I'l.AN    OF    ENOBINTES    AM»   OtTTWOB 

175...The  general  outline  of  tlic  enceinte  may  be  curvi- 
linear, or  a  polygonal  figure  of  any  character, 

17'-...Sy-ii  m  of  Fortification.  Although  an  infinite  diver- 
sity of  figures  may  thus  be  presented  in  the  outline  or  plan  of 
the  enceinte,  they  may  be  all  classed  under  four  heads,  to  each 
of  which  engineers  generally  have  applied  the  term,  system  of 
fortificatibn.  These  four  classes  are:  1,  the  dircular  or  cwrWr 
linear  system  ;  2,  the  polygonal  or  caponn'u"  r<-  system  ;  3,  the 
A  n i tilled  system  •  4,  the  bastiorud  sysU  m 

177.. .The  term  method  of  fortification,  instead  of  system,  "is 
now  usually  applied  to  the  manner  of  fortifying,  which  is  gen- 
erally prevalent  in  anjT  country  ;  or  to  the  mode  adopted  by 
any  individual,  as  the  German  method,     Y<iul>an'>s  method,  etc. 

178. ..Circular  System.  The  circular  system  consists  of  an 
enceinte,  the  plan  of  which  is  circular,  or  curvilinear. 

179. ..Polygonal  System.  In  the  polygonal  system,  the  plan 
is'either  a  polygon,  with  salient  angles  alone,  PL  8,  Fig.  72, 
each  side  of  which,  A  A,  is  flanked  by  a  casemated  capon- 
niere,  C,  placed  in  the  ditch,  D,  and  midway  between  the  two 
salients,  A  /  or  else  each  side  of  the  polygon  is  broken  in- 
ward at  the  centre,  so  as  to  form  a  slight  reentering,  PL  8, 
Figs.  73,  74,75,  76,  77,  to  procure  a  casemated  flanking  ar- 
rangement, F  F,  for  the  caponnieres,  C,  which  occupy  these 
reenterings,  and  also,  in  some  cases,  to  flank  works  in  advance 
of  the  enceinte. 

180.. .Tenailled  System.  The  tenailled  system,  PL  8,  Fig. 
78,  consists  of  a  tenailled  line,  the  reentering  angles  of  which 
are  between  90°  and  100°,  and  the  salient  angles  not  less  than 

<;o°. 

181...Bastioned  System.  The  bastioned  system,  Fig.  79, 
consists  of  lunettes  or  bastions  connected  by  curtains,  D  1), 
between  the  extremities  of  their  flanks,  B  D.  The  bastions 
usually  consist  of  two  faces  and  two  flanks,  the  scarps  of  each 
of  which  are  plane  surfaces.  In  most  of  the  older  fortifica- 
tions, and  in  a  few  of  the  more  recent  wTorks  in  Europe,  the 
flank  is  broken  ;  the  portion  of  it  at  the  shoulder  angle  form- 


i 

OUTWORKS    AND   DETACHED    WORKS.  73 

ing  a  projecting  mass,  which  is  termed  an  orillo?i,  whilst  the 
portion  between  the  orillon  and  the  enceinte  curtain  is  re- 
tired, or  brought  in  toward  the  interior  of  the  bastion,  and  is 
thus  partially  covered  by  the  orillon  from  fire,  except  in  the 
prolongation  of  the  enceinte  ditch.  In  some  cases  the  plan  of 
the  orillon,  as  well  as  that  of  the  retired  flank,  is  curvilinear ; 
in  others  they  are  both  rectilinear. 

182. ..Front  of  Fortification.  The  term  front  of  fortifica- 
tion is  applied  either  to  the  portion  of  the  enceinte  comprised 
between  the  capitals  of  two  adjacent  salient  angles  of  the  poly- 
gon, or  to  this  portion  and  any  other  works  within  or  beyond 
it  which  are  comprised  between  two  adjacent  capitals,  and  are 
connected  with  this  portion  by  relations  of  defence. 


OUTWORKS  AND  DETACHED  WORKS. 


183.. .A  work  consisting  of  an  enceinte  alone  is  more  or  less 
exposed  to  surprise,  as  it  must  have  outlets  of  some  descrip- 
tion to  keep  up  a  communication  with  the  exterior  and  a 
bridge,  or  other  means  for  crossing  the  ditch.  But  this  is  not 
the  only  defect  of  a  fortification  of  tins  simple  character;  for, 
having  no  cover.-  beyond  the  ditch  lor  it.-  garrison, their  action 
must  be  restricted  to  what  may  be  termed  a  passive  resistance 
alone;  as,  in  any  attempt  t<>  operate  on  the  exterior,  they  are 
exposed  to  lire  so  soon  as  they  emerge  from  the  ditch;  and  in 
a  ntnat  toward  the  work,  if  closely  pursued  by  the  assailant, 
thi'Y  will  not  only  run  tin-  nali  of  being  cut  oil",  but  a  reti 
under  such  circumstances  may  lead  to  the  capture  of  the  work 
10 


74  0!  rWOXtXfl    AM>   DETACHED    WOBSB. 

itself,  by  the  assailant  being  enabled  to  enter  with  the  retreat- 
ing force. 

L84:..*.To  provide  against  dangers  of  bo  grave  a  character, 
engineers  have  devised  other  defences  beyond  the  diteh.  and 
which  they  have  placed  in  Immediate  defensive  relations  with 
the  enceinte,  being  under  its  fire  and  in  positions  where,  if 
assaulted,  they  can  be  readily  succored  by  the  garrison.  To 
this  class  of  exterior  defences  the  term  outworks  has  been  ap- 
plied. The  works  which  come  under  this  head  are  the  COM  red- 
way,  the  tenaill%  the  <hmihn<>\  the  oourUerguard^  the  r<  doubt 
or  /•>'</>//'/.  the  1>  nii'ilhm*  the  Komwork  and  the  cr(nc)i-tr<>rk. 

l86.;.CovEEED-WAY.      The  eovered-wa v.  SB  its  name  imports, 

is  an  open  Corridor  or  passage,  masked  from  the  assailant's 

view  by  an  embankment,  which  borders  the  diteh  of  the  en- 
ceinte alone  when  there  are  no  other  outworks;  but,  in  the 
contrary  case,  also  envelops  the  ditches  of  these,  forming  thus 
a  continuous  covered  line  of  communication  around  the  for- 
tification. 

180. ..The  covering  embankment  itself  is  arranged  toward 
the  covered-way  like  an  ordinary  parapet,  and  it  receives  on 
the  exterior  a  gentle  slope  or  glacis.  By  this  arrangement  the 
garrison  have  a  covered  position  beyond  the  ditch  where  they 
can  assembly  with  safety,  either  for  the  purpose  of  making  a 
sortie  or  to  guard  the  ditches  and  the  communications  across 
them;  and  which  affords  them  also  a  secure  point  of  retreat  if 
repulsed  in  a  sortie,  as  a  reserve  left  in  the  covered-way  will 
be  at  hand  to. check  the  pursuit  by  their  fire,  and  enable  the 
retreating  party  to  gain  the  enceinte. 

187... Flatus  of  Aims.  The  covered-way,  from  the  direction 
given  to  the  counterscarps  of  the  enceinte  and  outworks,  forms 
a  line  of  communication  with  salient  and  reentering  parts,  Pis. 
8,  9,  Figs.  80  to  85.  The  salient  portions,  S,  are  termed 
ealii  n  f  places  of  arms ;  and  the  reentering  parts  the  reentering 
places  of  arms. 

188. ..The  salient  places  of  arms,  it  will  be  seen,  result  from 
the  general  plan  of  the  covered-way;  but  the  reentering  places 


OUTWORKS    AND    DETACHED    WORKS.  75 

of  arms  are  formed  by  changing  the  directions  of  the  two 
brandies  where  they  form  the  reenteringa,  i?,  so  as  to  make  a 
salient  within  the  reenteringe;  thus  enlarging  the  covered-way 
at  these  points,  and  procuring  a  flanking  arrangement,  by 
which  the  glacis  can  be  swept,  and  a  cross-fire  be  brought  to 
bear  on  the  ground  in  advance  of  the  salients. 

1  s'.'...Tkavi;ksks.  The  covered-way,  from  its  position  and 
the  usually  slight  command  given  to  the  crest  of  its  glacis,  is 
very  much  exposed  to  the  effects  of  an  enfilading  fire.  With 
a  view  to  remedy  this  defect,  and  also  to  enable  the  garrison 
to  dispute,  foot  by  foot,  the  possession  of  this  outwork  by  the 
ilant,  eartheni  masks,  formed  like  an  ordinary  parapet,  and 
termed  traverses,  are  thrown  up  across  it.  The  traverses 
usually  extend  to  the  counterscarp,  the  wall  of  which  is  built 
up  to  sustain  them.  At  the  end  toward  the  glacis  a  passagttj 
or  defile,  is  left  between  them  and  the  covering  embankment, 
to  admit  of  a  free  communication  throughout  the  covcred-wav. 

190...Texaillk.  The  tenaille  is  a  tow  work,  placed  in  the 
reentering  formed  in  the  enceinte  ditch  by  the  curtain  and 
flanks  of  the  bastioned  system,  being  isolated  by  a  ditch  be- 
tween it  and  these  parts  of  the  enceinte.  Its  chief  purpose  is 
to  serve  as  a  mask,  covering  the  scarp  walls  of  this  reentering 
from  tire,  ib  well  as  the  Outlets  to  the  enceinte  ditch,  which  are 
usually  placed  in  the  centre  of  the  curtains. 

L 91... The  tenaille  has  received  various  forms  from  engineers. 
In  some  cases  it  has  been  made  with  two  laces  or  wil 
making  a  reentering  angle  opposite  the  centre  of  the  enceinte 
curtain.  In  others  the  two  wing-,  instead  of  being  proloi 
until  they  meet,  are  connected  by  a  abort  curtain  parallel  to 
that  of  the  enceinte.  In  some  examples,  it  has  the  form  of  a 
small  bastioned  front.     In  others,  it  <■  ftwo  flanks  i 

ted    by  a   curtain.      Tie-   think.-    in    some    cases    have    b 

mated   for  guns    and   mortars.     Tin    b  i  aill<    ;-   asually 
revetted  with  masonry,  both  in  front  and  rear.     In  sou 

the  emb  atone,  toward  the  Hanks  of  the  enceinte,  an   revetted, 


76  OUTWORKS    \N"    DETACHED   WORKS. 

the  intermediate  portions  consisting  of  an  ordinary  earthen 
parapet,  without  either  scarp  or  gorge  wall. 

r.'i\..i>iMiu  \r.    The  demilune,  PL  9,  Figs.  81,  82,  S3.  E 
A.irk  in  the  form  of  a  redan,  P.  placed  in  front  of  the  en* 

eeinte  curtain,  which  it  masks  from  fire,  as  well  as  a  portion  of 
cadi  face  of  the  enceinte,  at  the  shoulder  angles  of  the  bas- 
tions. It  is  isolated  from  the  enceinte  by  the  main  ditch,  and 
from  its  own  covered-way  by  its  ditch.     From  its  importance: 

the  scarp  and  gorge  of  the  demilune  are  generally  revetted, 
though  in  Some  cases  the  reveteinelit  has  heeii  omitted*. 

193...Cor.\Ti:i;(,r.\i:i>.  The  OOUnter'guard  is  an  isolated  work, 
< '.  Fig.  83,  in  the  form  of  a  redan,  which  envelops  the  faces  of 
a  hastioft.  In  some  cases  it  consists  simply  of  an  earthen  mask 
having  the  profile  of  an  ordinary  parapet;  but  it  is  usually 
revetted  botli  in  front  and  rear. 

194.. .Redoubts.  The  term  redoubt,  or  reduit,  is  applied  to 
outworks  placed  within  other  outworks;  their  object  being  to 
strengthen  the  defence  of  the  principal  work. 

195... A  work  of  this  class  is  usually  placed  within  the  demi- 
lune, and  is  termed  the  demilune  redoubt.  Small  works  of 
this  kind  are  also  placed  in  the  salient  and  reentering  places  of 
arms  of  the  covered-way,  and  are  termed  the  redoubt  of  the 
salient)  or  reentering*  place  of  arms.  These  redoubts  are,  in 
some  cases,  simple  earthen  works  ;  in  others,  they  are  revetted  ; 
and  in  others,  casemated,  both  for  the  service  of  artillery  and 
small  arms. 

IOC.Tknaillon.  The  term  tenaillon,  PI.  9,  Fig.  81,  is  ap- 
plied to  a  kind  of  face  cover,  or  conntergnard,  rl\  of  the  demi- 
lune. It  is  only  to  be  met  with  in  some  of  the  old  fortified 
places  of  Europe,  ami  was  added  to  give  more  strength  to  the 
fronts  where  the  demilune  was  too  small. 

197...IIokn\\okk.  The  hornwork,  PI.  9,  Fig.  82,  usually 
consists  of  a  hastioned  front,  II,  with  the  ordinary  outworks, 
having  two  long  branches,  F I\  or  wings,  which  rest  upon  two 
adjacent  bastions,  or  two  adjacent  demilunes,  D  IJ,  of  the  en- 
ceinte— its  covered-way  forming,  with  that  of  the  enceinte,  a 


OUTWORKS    AND    DETACHED    WORKS.  77 

continuous  line  of  communication.  The  object  of  this  outwork 
is  to  strengthen  a  salient  or  other  weak  portion  of  the  enceinte 

198...Ck<>\v\-\vork.  The  crown-work,  PI.  9,  Fig.  83,  con- 
sists of  two  or  more  bastioncd  fronts,  C,  with  their  outworks, 
placed  in  front  of  Borne  portion  of  the  enceinte,  to  give  it  addi- 
tional strength.  It  is  terminated,  like  the  hornwork,  by  two 
wings,  F  F,  which  rest  either  ffpon  the  enceinte,  or  upon  the 
demilunes,  D  D.  Its  covered-way,  like  that  of  the  hornwork, 
forms  a  continuous  communication  with   that  of  the  enceinte. 

19 9... Detached  Works.  There  are  two  other  classes  of  ex- 
terior defences  besides  the  outworks,  termed  detached  works 
and  advema  d  uwk»„  the  object  of  which  is  either  to  strengthen 
some  weak  portion  of  the  enceinte  or  to  occupy  positions 
which  would  be  of  advantage  to  an  assailant  in  his  attacks  on 
the  enceinte. 

300... Detached  works  are  such  as  are  placed  beyond  the 
covered-way  of  the  enceinte,  but  within  the  range  and  support 
of  its  lire.  Advanced  works  are  such  as,  from  their  advanced 
ion.  receiving  but  little  or  no  support  from  the  fire  of  the 
enceinte,  must  rely  Upon  their  own  resources  for  defence. 
The  former  class  are  usually  open  in  the  rear,  so  their  interior 
may  be  exposed  to  the  fire  of  the  enceinte  ;  whilst  the  latter 
should  be  closed  throughout  and  of  sufficient  strength  of  pro- 
lile  to  secure  them  from  an  open  assault. 

201...In  PI.  9.  Fig.  si.  is  a  detached  work,  /..flanked  by 
the  demilunes,  I>.  of  the  enceinte.  The  plan  of  this  work  tea 
lunette,  with  its  covered-way  and  places  of  arms,  R  and  &. 


7^  INTKRIOR     RETRf.XCHMKXT^. 


INTERIOR    RETRENCHMENTS. 


202. ..Besides  the  works  exterior  to  the  enceinte,  the  object 
of  which  is  to  retard  the  assailant  in  his  attempts  to  enter  it 
by  breaching1,  engineers  have  placed  within  it  other  works 

which,  in  some  cases,  are  designed  simply  to  enable  the  gar- 
rison to  make  an  effectual  defence  of  the  breach,  when  the 
assault  upon  it  is  made,  and  give  them  a  secure  point  of  re- 
treat and  safety  when  driven  from  it ;  and  in  others,  these 
interior  works  arc  chiefly  designed  to  bring  a  plunging  lire  to 
bear  on  the  assailant's  siege  works  exterior  to  the  enceinte. 
The  former  class,  intended  for  the  defence  of  the  breach  alone, 
arc  termed  interior  retrenchments  I  and  the  latter,  awdlierf. 

^0-°.... Interior  retrenchments  are  either  placed  within  the 
bastions,  -which  are  the  parts  of  the  enceinte  usually  breached, 
or  in  rear  of  their  gorges.  Those  which  are  placed  within  the 
bastions  extend  across  them,  either  between  the  faces  or  be- 
tween the  flanks.  When  placed  at  the  gorge,  they  connect 
the  two  adjacent  curtains. 

204.. .The  plan  of  these  works  varies  with  their  position,  the 
size  of  the  bastions,  or  the  more  or  less  of  openness  of  their 
salient  angles. 

205. ..In  small  bastions  with  acute  salients,  when  the  re- 
trenchment rests  upon  the  faces,  it  usually  receives  the  form 
of  a  tenaille  or  inverted  redan,  the  angle  of  the  tenaille  being 
about  100°.  When  the  bastions  are  large  and  the  salient 
angle  quite  open  or  obtuse,  the  retrenchment  may  receive  the 
form  of  a  small  bastioned  front,  PI.  9,  Fig.  85,  resting  upon 
the  faces. 

206. ..Either  of  these  forms  may,  in  like  manner,  be  used, 


BASTIONED    SYSTEM.  79 

when  the  retrenchment  rests  upon  the  flanks  of  the  bastion. 
But  as  this  position  enables  a  retrenchment  of  the  form  of  an 
ordinary  redan  to  hare  its  ditches  swept  by  the  fire  of  the 
flanks  of  the  adjacent  bastions,  this  form  is  in  some  cases  used 
in  preference. 

207... When  placed  between  two  curtains  at  the  gorge  of  a 
bastion,  the  plan  of  the  entrenchment  is  always  a  bastioned 
front. 

20S... Cavaliers  are  placed  either  upon  the  curtains  or  within 
the  bastions.  The  latter  is  the  more  usual  position  selected 
for  them.  Their  plan  in  this  position  is  usually  that  of  a 
lunette,  the  faces  and  flanks  of  which  are  parallel  to  those  of 
the  enveloping  bastion.  Cavaliers  receive  a  considerable  com- 
mand over  the  parapet  of  the  enceinte,  and  in  some  cases, 
they  are  arranged  with  a  tier  of  casemated  fire,  above  which 
is  an  open  battery. 

209. ..Interior  retrenchments  are  usually  constructed  with  a 
revetted  scarp  and  counterscarp,  to  secure  them  from  an  open 
assault;  and,  in  some  cases,  a  covered-way,  with  a  small  reen- 
tering place  of  arms,  fi,  PI.  9,  Fig.  85,  closed  by  traverses,  is 
arranged  in  advance  of  the  ditch,  to  insure  the  safe  retreat  of 
the  garrison  when  driven  from  the  breach. 


BASTIONED   SYSTEM. 


HO.. .A    bastioned  enceinte  consists  ofs  of  bastions 

which  occupy  the  salient  angles  <>f  the  polygon,  within  which 
the  enceinte  is  enclosed;  the  thinks  of  the  bastions  being 
usually  connected   by  straight  curtains. 

211. ..The  sides  of  the  polygon  which  connect   the  salienl 


BO  i;.wil"NU»   BYB1  : 

angles  of  the  bastions,  are  termed  the  anterior  sides,  in  contra* 
<li.-tiiicti.in  to  the  sides  of  an  interior  polygon,  which,  being 
parallel  to  tin*  first  ami  occupying  the  positions  of  the  curtains, 
arc  termed  the  interior  sides. 

212...The  l»a>ti<incil  enceinte,  when  its  relict'  and  plan  are 
suitably  arranged,  possesses  the  advantage  of  having  its 
ditches  thoroughly  swept  from  within  the  enceinte  itself, 
thus  securing  the  flanking  arrangement  of  the  scarp,  whilst 
the  garrison  also  is  kept  within  the  enceinte  under  the  imme- 
diate eye  and  orders  of  their  commander,  up  to  the  moment  of 
the  fall  bf  the  work  ;  of  bringing  a  cross  and  Hank  fire  to  bear 
upon  the  approaches  on  the  BalientS  of  the  enceinte  in  the  di- 
rections of  the  capitals  of  the  bastions:  and  furnishing  a 
strong  direct  and  cross  tire  upon  the  site  in  advance  of  the 
curtains  and  the  faces  of  the  bastions. 

213.. .The  principal  objections  urged  against  the  bastione,d 
kem  arc,  that  its  chief  characteristic — a  perfect  flanking 
disposition  for  the  entire  line  of  the  scarp — is  attainable  only 
under  certain  relations  between  the  requisite  relief  for  a  per- 
manent Work  and  the  length  of  the  exterior  side  and  curtain, 
which,  therefore,  restricts  it  in  its  application  to  fortification 
of  a  permanent  character;  that,  in  order  to  secure  sufficient 
length  of  Hank  for  an  effective  thinking  disposition,  the  angle 
between  the  face  of  the  bastion  and  the  exterior  side,  termed 
the  diminished  angle  of  the  polygon,  has  to  be  made  so  great 
as  to  decrease  considerably  the  space  enclosed  within  the  poly- 
gon, whilst  the  development  of  the  line  of  the  enceinte  is 
-really  increased  by  it;  that  this  direction,  necessarily  given 
to  the  faces  from  this  cause,  throws  their  prolongations  in  po- 
sitions very  favorable  to  the  erection  of  enfilading  batteries 
against  them  ;  that  the  flanks,  upon  which  the  whole  system  is 
based,  lie  in  positions  in  which,  like  the  faces,  they  can  be  not 
only  ea>ily  enfiladed,  but  are  further  exposed  to  a  reverse  tire 
from  shot  which  may  pass  over  the  parapet  of  the  faces  as  well 
ab  the  opposite  flank  ;  and  that  these  objections  are  the  stronger 


vaui:anV  first  method.  81 

as  tlic  salient  angles  of  the  polygon  are  smaller.  0T  as  tlio  nuni- 
ber  of  sides  is  decreased. 

214.. .Besides  these  objections,  •which,  to  a  certain  extent,  arc 
well  founded,  where  the  defensive  arrangements  arc  chiefly 
open,  as  is  the  case  in  most  land  fronts,  others  have  been 
urged  against  this  system,  which,  being  rather  of  a  compara- 
tive character,  a-  showing  the.  advantages  of  other  systems 
<>ver  this,  will  besl  l»e  examined  elsewhere. 

215. ..As  the  plan  and  relief  of  the  hastioned  enceinte,  em- 
ployed among  engineers  of  the  present  day,  differ  in  no  very 
material  points  from  those  Adopted  about  the  period  of  Van- 
han,  when  the  art  of  fort  iti eat  ion  assumed  somewhat  less  of 
mere  mechanical  routine,  it  has  hecome  the  practice  in  mili- 
tary schools  in  Europe  to  deduce,  from  the  description  of  the 
bastioned  method  of  Vauban  ami  his  immediate  snccessoTS, 
the  principles  upon  which  the  tonus  and  dimensions,  both  of 
the  enceinte  and  its  outworks,  as  well  as  their  defensive  rela- 
tions, are  based.  As  this  course  has  the  farther  advantage  of 
exhibiting  the  views  of  men  who  are  still  looked  to  as  the  safest 
authorities  in  the  art,  whilst  it  gives,  at  the  same  time,  a  his- 
tory of  it-  progress  and  changes  from  the  period  when  it  may 
he  said  to  have  first  broken  loose  from  the  trammels  of  mere 
routine  up  to  the  present  day,  it  has  heeii  also  adopted  as  the 
ha>is  of  the  instruction  given  on  this  subject  in  this  institution. 


V.W  HAYS    FIRST   METHOD. 


216.. .Vauban  1  -  of  three  different  methods 

in  the  places  planned  by  him.     The  Fortress  of  V 
fortified  after  his  third  method;  |  Landau  and    l;< 

11 


Eft)  v.u  BAJj'fl    PTB8T  VETHOD. 

alter  his  second:  but  the  greater  pari  of  the  places  fortified  by 
him  are  planned  according  to  his  first,  or  earliest  method.    . 

L'17...N-.ii:.  In  the  following  description  of  the  methods  Of 
Vauban,  Oormontaingne  and  some  other  French  authors,  the 
English  yard  has  been  substituted  for  the   French  Jni{f  toi* 

and  the  )mir<\  each  of  which  is  so  nearly  the  equivalent  of  the 
vard  as  not  to  affect  in  any  sensible  manner  the  principles  Of 
the  defensive  relations  of  the  parts.  In  like  manner  the 
English  foot  lias  been  substituted  for  the  French  toot. 

L'l>...ri;.>Mi.i;  <>i-  Knckimi:.  In  the  profile  of  this  method, 
Fig.  1,  PI.  1,  the  scar])  Mall  is  3<i  feet  high,  its  slope  beingfive 
perpendicular  to. one  of  base;  surmounting  this  is  another  wall 
from  4  to  t!  feet  high,  the  object  of  which  is  to  sustain  the  ex- 
terior of  the  parapet.  The  parapet  is  18  feet  thick,  the 
superior  slope  being  1-9;  the  interior  crest  is  8  feet  above  the 
terreplein,  which  is  42  feet  in  width.  The  mean  command  of 
the  interior  crest  above  the  site  is  about  26  feet.  The  bottom 
of  the  ditch  is  about  17£  feet  below  the  site. 

2i;,...I>i..\.\  of  Knckixti:.  Vauban  adopted  no  arbitrary  or 
invariable  combination  of  parts  in  his  methods.  His  greal  ex- 
cellence as  an  engineer  is  shown  in  the  acknowledged  skill 
with  which  he  adapted  the  fortifications  he  planned  to  the  de- 
fensive  requirements  of  the  sites.  Selecting  long,  medium,  or 
short  exterior  side.-,  and  varying  the  lengths  and  directions  of 
the  faces  and  flanks  so  as  to  procure  the  best  command  over 
the  exterior  ground,  and  to  withdraw  these  parts  from  the  en- 
filading views  of  the  assailant.  In  his  works,  however,  he  has 
generally  taken  360  yards  as  the  greatest  limit  of  the  exterior 
side;  the  perpendicular  of  the  front  £  when  the  polygon  is  a 
square;  1-7  for  the  pentagon;  and  1-6  for  all  higher  polygons. 
With  thes»  starting  points  he  procured  diminished  angles 
which  eave  more  than  00°  to  the  salient  angles  of  the  bastions 
in  all  cases,  and  thinks  of  suitable  length  both  to  flank  the 
main  ditch  and  to  encounter  with  advantage  the  counter-bat- 
teries which  could  be  erected  against  them.  The  following- 
constructions,  both  for  the  enceinte  and  outworks,  are  taken 


yatban's   FIRST   MKTIIOl).  83 

from  the  best  French  authorities  as  adopted  by  hltn  for  poly* 
gens  higher  than  the  pentagon. 

220...In  the  plan  or  t/togd,  Pig.  2,  PL  1,  the  magistral  is 
taken  as  the  directing  line;  the  exterior  side  is  860  yards;  on 
the  perpendicular  of  the  Front  a  distance  of  1-6  the  exterior  side 
is  set  off;  lines  drawn  through  this  point  and  the  extremities 
of  the  exterior  side,  determine  the  directions  of  the  faces  and 
the  lines  of  defence ;  from  the  salients  a  distance  equal  to  8-7 
of  the  exterior  side  is  set  oft*,  which  gives  the  lengths  of  the 
faces  and  the  positions  of  the  shoulder  angles;  the  flank  \% 
drawn  by  taking  the  opposite  shoulder  angle  as  a  centre;  and 
with  a  radius  equal  to  the  distance  betweeri  the  shoulder 
angles,  describing  an  arc  to  intersect  the  line  of  defence,  the 
chord  oi  this  arc  is  the  flank;  the  curtain  is  drawn  by  joining 
the  extremities  of  the  flanks.  By  this  construction  the  flanks 
will  be  about  54  yards;  the  curtain,  14<i;  and  the  lines  of  de- 
fence. 267 — the  length  of  these;  being  determined  so  that  the 
salients  of  the  bastions  can  he  defended  with  the  rampart  yun, 
or  wall-pi 

L'-Jl...Ti.\  \iua-:.     In  many  of  the  places  constructed  before 
Vauban's  time  there  was  a  low  work,  enveloping  the  enceinte 
and    connected   with  it,  called  a  faueeo-braie.     This  work, 
which  had  many  defects,  was  suppressed  by  Vauban,  who  was 
the  first  to  use  the  tenaille  in  its  place.     The  tenaille  has 
many  valuable  properties:  it  covers  the  arched  communica- 
tion, or  postern,  under  the  curtain  :  masks  the  masonry  of  the 
curtain  and  flanks,  so  that  a  breach  cannot  lie  made,  in  them, 
and  in  this  way  prevents  retrenchments,  resting  against  tl 
parts,  from  being  turned;  a  place  of  arms  is  formed  betv 
it  and  the  curtain,  where  troops  can  be  assembled  for  BOl 
in  the  ditches;  finally,  its  Are  sweeps  the  ditch  and  counter* 
p,  and  helps  to  cover  the  retreat  of  troops  from  the  other 
outworks.    The  tenaille  is  separated  from  the  curtain  by  l 
ditch  10  yards  wiae,  and  from  the  thuds-  by  ditch 
The  form  of  the  tenaille,  as  Deed  by  Vauban,  w  ible: 

in  .-  made  it  with  a  curtain  and   two  small   fla 


84  v.ur,\N--    I  \\:<T   Minion. 

parallel  to  those  of  the  enceinte;  in  others,  it  consisted  simply 
of  two  wings  placed  on  the  prolongations  of  the  faces;  and, 
finally,  he  gave  it  the  form  in  I'iir.  2,  with  a  small  curtain 
and  two  wings,  which  is  the  one  at  presenl  most  generally 
adopted.  The  relief  of  the  tenaille  i>  bo  arranged  as  not  to 
mask  t lie  fire  of  the  flanks  on  the  ditch  of  the  enceinte 
along  the  faces;  for  this  purpose  Yaul>an  places  its  interior 
crest  on  a  leva]  with  the  site,  or  a  Little  below  it. 

222...]&un  Ditch.  Vauban  followed  no  invariable  rule  in 
Regulating  the  dimensions  of  the  enceinte  ditch  ;  its  most  usual 
width  at  the  salients  of  tin-  bastions,  where  the  counterscarp  is 
an  arc  of  a  circle,  is  about  "><>  yards  ;  the  rest  of  the  counter* 
scarp  is  tangent  to  this  arc,  and  directed  upon  the  opposite 
shoulder  angles. 

223...Di:mili  m:  am>  Redtjtt.  Vauban  increased  the  dimen- 
sions of  the  demilune  which  had  been  used  previous  to  his 
time.  The  object  of  this  work  is  to  secure  the  gates  of  the 
place  from  a  surprise  ;  to  mask  from  the  enemy's  batteries  the 
flanks  and  curtain  of  the  enceinte;  and  give  cross  fires  on  the 
salients  of  the  bastions.  The  plan  and  dimensions  of  the 
demilune  vary  also  in  Vaiiban's  works.  It>  magistral  is  gene- 
rally laid  out  by  taking  a  point  on  the  bastion  face  at  LO  yards 
from  the  shoulder  angle,  and  drawing  a  line  from  this  point  to 
the  perpendicular  of  the  front,  so  as  make  the  face  of  the 
demilune  equal  to  2-7  of  the  exterior  side.  The  parapet  of 
the  demilune  is  the  same  as  that  of  the  enceinte  ;  its  command 
feet  Less  than  that  of  the  enceinte.  All  the  outworks  in 
tlii,-  system  are  commanded  by  the  enceinte;  the  outworks 
most  advanced  being  also  commanded  1>£  those  in  rear. 

224...To  strengthen  the  demilune,  and  secure  for  the  troops 
entrusted  with  its  defence  a  safe  retreat  when  it  is  carried, 
Vauban  placed  in  it  a  small  redoubt.  This  work,  in  some  in- 
stances, was  only  a  simple  <-r<  not*  d  waUy  with  a  ditch  in  front ; 
sometimes  it  was  made  of  earth,  and  after  tne  commencement 
of  thi'  siege. 

L'25...The  ditch  of  the  demilune  is  generally  about  24  yards 


vauban's  first  method.  85 

wide,  and  of  the  same  depth  as  that  of  the  enceinte;  its  coun- 
terscarp and  that  of  the  enceinte  forming  a  continuous  wall. 

226...Covebed-way.  The  covered-way  envelops  the  entire 
counterscarp.  Vauban  placed  a  high  value  on  this  Work, 
which,  to  use  his  own  words,  "  Costs  less  to  the  defence  and 
mote  to  the  assailant  than  any  other  work."  The  covered-way 
prevents  all  access  to  the  ditch,  by  a  strong  fire  of  musketry, 
which  sweeps  all  tiie  exterior  ground ;  it  is  a  secure  position, 
where  tnx.ps  can  be  assembled  in  safety  for  sorties;  it  covers 
the  retreat  of  troops  from  the  exterior  into  the  other  works. 
The  general  width  of  the  covered-way  is  12  yards.  To  set  out 
the  reentering  place  of  arms,  two  points  are  taken  at  20  yards 
fn.ni  the  reentering  angle,  made  by  the  interior  crests  of  the 
covered-ways  of  the  demilune  and  bastion,  and  upon  tl 
crests,  and  from  these  points  as  centres,  with  radii  of  21  yards. 
arcs  are  described  ;  the  point  of  their  intersections  being  joined 
with  their  centres,  gives  the  crests  of  the  reentering  place  of 
arms.  The  parapet  of  the  covered-way  is  terminated  in  a 
glacis,  the  foot  of  which  is  from  40  to  :,n  yards  from  the  inte- 
rior crest 

L'l'7...Ti:  wi  B8E8.     To  close  the  place  of  arm.-,  and  enable  the 
troops  to  defend  the  covered-way  foot  by  foot,  trav 
earth    formed  into  parapets  are    placed    at  the  places  of  arms. 
Defiles  ory  •    I  ■     •  are  left  between  the  traverses  and 

the  crest  of  the  covered-way,  for  the  circulation  of  the  troops* 

The  covered-way  is  palisaded  to  prevenl  surprise. 

228.. .Communications.  The  oommimieaUons  constitute  an 
important  part  of  every  system.  In  Vauban's  front,  ramps 
are  mad<  end  from  the  plane  of  Bight  to  the  fc  rreplein, 

A  postern  is  made  under  the  curtain,  to  communicate  from  the 
interior  with  the  ditch;  another  postern  is  made  under  the 

tenaille.  to  lead    to  the   demilune  ;  a   doubl  .which 

i^  a  by  a  parapet  terminated  in  a 

glacis  toward  the  ditch,  nmunication  through 

the  ditch  to  the  gorge  of  the  demilun    .  are 

placed  in  the  ditch  of  the  demilune,  and  cover  th<  ryin 


86  vaiuan'-   RB81    mi  in-. n. 

the  enemy's  fire  through  its  ditch  :  stairs  are  placed  :it  the 
gorges  of  the  tenaille  and  demilune,  and  along  the  counter* 
p  at  the  places  of  arms,  to  ascend  from  the  ditch  to  the 
berrepleins  oi  those  works.  To  communicate  with  the  exte- 
rior, narrow  openings  are  made  in  the  faces  of  the  reentering 
place  of  arms,  to  lead  from  the  terreplems  to  the  glacis;  they 
are  termed  soriu  passages,  or  sally-ports,  and  arc  closed  by 
barriers. 

IIKMAKKS. 

229... Enceinte.  In  the  trage  adopted  by  Vauban  for  the 
enceinte,  it  may  be  observed  that  the  Length  and  positions  of 
the  lines  of  the  front  resulting  from  it  are  in  good  defensive 
relations,  both  for  cannon  and  small  arms. 

230...In  the  lirst  place,  the  foot  of  the  scarp,  throughout  the 
Length  of  the  curtain  and  the  bastions,  is  thoroughly  expos  1 
to  the  lire  of  the  flanks,  which^  from  the  diminished  angle  as- 
sumed in  the  hexagon  and  higher  polygons,  which  [s  about 
L8^°,  and  the  curtain  angle,  which  is  nearly  100° — can  sweep 
both  the  curtain  scarp  and  that  of  the  bastion  lace  from  an 
embrasure  placed  at  die  curtain  angle. 

231. ..In  the  second  place,  the  length  of  the  flank  is  sufficient 
to  contain  as  many  cannon,  at  least,  as  the  assailant  can  place 
to  counter-batter  the  flank  from  the  glacis  crest  opposite  the 
flank ;  and  the  flank  can  also  bring  an  efficient  lire  of  small 
arms  to  hear  on  this  battery  of  the  assailant. 

232...The  bastions  are  of  good  Bize,  and  would  admit  of  effi- 
cient interior  retrenchments  being  thrown  up  in  them,  although 
Vauban  does  not  indicate  this  auxiliary  means  in  his  1st 
Mi  thod. 

238...T)  naii.i.k.  Vauban  substituted  the  tenaille  for  the 
fau8S6-braie,  as  this  latter  work  facilitated  an  escalade,  and, 
moreover,  exposed  the  troops  in  it  to  the  annoyance  of  the 
splinters  from  the  walls  behind,  when  exposed  to  the  assail- 
ant's lire.  The  tenaille  was  devised  mainly  to  mask  the  scarp 
wall  of  the  curtain  and  Hanks,  whilst  its  relief  was  so  regulated 


v.\r i:\.\V    REST   METHOD.  s7 

as  not  to  intercept  the  fire  of  the  flanks  oa  the  enceinte  ditch 
before  the  bastion  faces.  The  plan  of  the  earlier*  tenaillea  con- 
sisted of  two  flanks  connected  by  a  curtain,  which  were  paral- 
lel to  the  same  lines  of  the  enceinte  Tliis  form  was  subse- 
quently abandoned,  as  the  flanks  were  found  to  be  exposed  to 
both  an  enfilading  and  reverse  fire  from  the  assailant's  positions 
in  front  of  the  enceinte;  and  the  one  now  in  most  general  USS, 
consisting  either  of  two  wings  Bimply,  or  of  two  wings  con- 
nected by  a  short  curtain,  adopted  in  its  place. 

The  tenaille,  however,  only  partially  subserves  its  object,  as 
it  does  not  cover  the  entire  height  of  the  scarp  of  the  enceinte 
curtain  and  flanks;  and,  what  is  a  more  serious  defect,  it 
leaves  the  entire  height  of  scarp  of  thai  portion  of  the  curtain 
opposite  to  the  ditch,  between  the  tenaille  and  the  bastion 
flank,  entirely  exposed  from  the  same  position,  and  liable  to  be 
breached. 

'J- }...lh  Mii.rxi:.  From  the  small  size  of  this  work,  it  irives 
hut  little  cover  to  any  portion  of  the  enceinte  except  the  cur- 
tain. It  is  not  sufficiently  thrown  to  the  front  to  give  a  good 
volume  of  cross  fire  on  the  glacis  in  advance  of  the  bastion 
salients;  and  the  reentering  formed  at  this  point,  by  the  two 
adjacent  demilune.-.  i.».  from  the  same  cans',  shallow,  and  of 
hut  little  strength.  Owing  to  this  last  defect,  the  assailant  can 
easily  breach  and  storm  the  enceinte  at  the  same  time  as  the 
demilune. 

Besides  these  defects,  the  demilune  is  not  provided  with  a 
permanent  reduit — a  work  necessary  to  enable  the  demilune 
to  make  a  vigorous  defence,  by  the  support  it  affords  the  as- 
sailed. 

1        bed-way.     From  the  width  given  to  the  demiln 
ditch,  the  covered-**  lanf   reverse  tire. 

from  which  they  are  hut  badly  screened  by  the  trav<  i 
Their  command  over  the  site  -  too  little.     Their  main 

defect,  ;  n  to  the  n  enterii 

this  important   position 


**VJ 


88  VAUBA2T8   THIRD    METHOD. 

mbling  troops  far  Borties  by  b  permanent  rddnit,  by  which 
any  open  attack  of  the  covered-way  could  be  prevented. 

236...Dm  1:1  b.  The  dimensions  given  both  the  enceinte  and 
demilune  ditches  present  a  formidable  obstacle  to  an  open 
assault,  ami  render  the  assailant's  passage  of  the  ditch  by  the 
more  difficult.  Tin-  demilune  ditch,  however,  offers  a 
wide  opening,  through  which  the  scarp  of  the  bastion  face  can 
be  Been  down  to  it,-  fool  from  the  assailant's  batteries  on  the 
glacis  crost  in  the  prolongation  of  the  demilune  ditch. 

•_'.".7...C"MMr.\i<  ations.  The  communications  within  the  en- 
ceinte, and  from  it  to  the  main  ditch,  are  sufficient  and  con- 
venient forthe  character  of  the  defence  designed.  Those  of 
the  outworks  are  for  the  most  part  narrow,  inconvenient  and 
badly  screened  from  the  assailant's  tire,  and.  therefore,  do  not 
furnish  a  good  provision  for  an  active  defence  beyond  the 
enceinte. 

238.. .Profiles.  The  great  command  over  the  site,  and 'the 
high  relief  given  to  the  enceinte,  are  very  much  in  favor  of  the 
defence,  both  as  to' the  effect  of  the  fire  on  the  assailant's  ap- 
proaches, and  for  security  against  an  escalade.  But)  in  attain- 
ing these  objects,  Vanban  has  left  exposed  to  the  assailant's 
distant  lire  a  considerable  portion  of  the  scarp  wall,  which, 
being  destroyed,  would  lay  the  enceinte  open  to  a  surprise. 


VAUBAiYS  THIRD  METHOD. 


239...In  his  3d  Method,  PI.  H,  which  differs  from  his  2d 
only  in  some;  minor  mollifications,  Vanhan  adopted  what  may 
he  termed  a  double  enceinte,  the  interior  one  being  continuous, 

and  consisting  of  small  easemated  hastioned  towers,  X,  A',  0, 


vat •  p. ax's  third  method. 

placed  at  the  angles  of  the  polygon,  which  are  connected  by 
curtains,  /',  Z,  IF,  IP,  in  the  form  of  bastioned  fronts,  the 
flanks  of  which  are  also  casemated,  and  intruded,  with  those 
of  the  towers,  to  sweep  the  ditch  of  this  enceinte. 

240...The  second,  or  exterior  enceinte,  is  not  continuous,  but 
consists  of  large  bastions,  A,  II,  K,  or  oounterguards  with 
flanks,  which  cover  the  towers  and  the  faces  of  the  bastioned 
curtain  between  them,  and  of  a  tenaille,  which  lies  between 
the  flanks  of  the  counterguards  and  covers  the  curtain  of  the 
interior  enceinte. 

241. ..In  advance  of  this  exterior  enceinte  is  placed  a  demi- 
lune, arranged  with  flanks,  which  contains  a  small  revetted 
redoubt,  and  a  covered-Wfty  similar  to  the  one  in  his  1st 
Method. 

•_>  I  •_'...  Pi.w.  The  lines  joining  the  salients  of  the  counter- 
guards  form  the  exterior  sides,  and  are  taken  at  360  yards. 
Tlie  perpendicular,  0  D,  is  one-sixth  of  the  exterior  side,  or 
60  yards.  The  face.  J  fft  one-third  the  exterior  side,  or  120 
yards.    The  flank.  //  h\  is  constructed  as  in  the  1st   Method. 

LM.°)...Tlie  tenaille  Consists  simply  of  two  wings  in  the  pro* 
longation  of  the  faces  of  the  oounterguards;  a  ditch  L0  yards 
wide  is  left  between  the  tenaille  and  the  flanks  of  the  counter- 
guard.  Hie  gorge  line  of  the  tenaille  and  the  flanks  of  the 
eonoterguards  lie  on  the  line  L  J/,  joining  the  salients  of  the 
towers. 

844...To  set  out  the  tower- and  connecting  curtain, aline, 
.V  '/'.  is  drawn  parallel  to  I.  .)/.  and   at  16  yards.     The  fiai 
//.  (j.  of  the  towera  are  drawn  through  points  /'.  at   11  yards 
from  .V.    The  portion  of  the  flank-.  /'.  /,'.  exterior  to  the  cur- 
tain, being  12  yards,  and  the  interior  portion,  /'  Q}  - 
The  bees  are  found  by  joining  the  points  /..  //. 

L'i:>...Tii.'  perpendicular,  T  T\  of  the  bastioned  curtain  is 
1"  yards.  The  flanks,  if,  FT,  are  on  the  prolongation!  of  the 
count. Ti/uard  flanks.     The  curtain,   W   f .  ie  parallel  to  /,   M. 

■  ructed  l>v  de- 
scribing an  arc  from  < 
L2 


90  VAUBAN's    iiiii:i>   KBTHOD. 

and  drawing  a  tangent  to  this  arc  from  the  point  correspond- 
in-'  to  /.  on  the  opposite  flank,  to  Z  H  . 

249.. .The  salient,  C\  of  the  demilune  is  at  110  yards  from 
the  point  0,  where  a  line  parallel  to  the  counterguard  bee, 
•and  .'in  yards  from  it,  cuts  the  perpendicular  of  the  front.  The 
demilune  face,  C  F' ,  is  96  yards,  and  ranges  on  a  poinl  />'.  at 
80  yards  from  the  point  JET.  The  flank,  F*  granges  pn  a 
point  at  2  yards  from  the  poinl  //,  and  is  terminated  on  the 
counterscarp  of  the  exterior  enceinte,  which  is  drawn  front 
a  point  j??,  at  G  yards  from  O,  tangent  to  an  arc  described 
from  A,  with  a  radius  of  30  yards. 

218. ..The  salient  of  the  demilune  redoubt  is  at  4(5  yards 
from  the  point  O.  The  face  of  the  redoubt  is  30  yards,  and 
parallel  to  that  of  the  demilune;  its  flank,  G'  11',  is  also  par- 
allel to  that  of  the  demilune. 

249. ..The  demilune  ditch  is  20  yards,  and  that  of  the  redoubt 
is  12  yards.  The  general  arrangement  of  the  covered-way  is 
the  same  as  in  the  1st  Method. 

250...Pbofd  bs.  The  profiles  of  the  interior  enceinte  and  of 
the  demilune  redoubt  are  alike,  as  shown  on  C  D" ;  and  tlu.se 
of  the  COUntergard  and  demilune  are  the  same  as  shown  ou 
E"  F". 

251.. .The  parapets  of  the  towers  are  of  stone,  the  flanks 
being  pierced  with  two  embrasnres.  The  flanks  of  the  ease- 
mates  are  also  pierced  for  two  guns.  The  centre  of  the  tower 
is  occupied  by  a  stone  traverse.  The  casemated  flank  Z  II'.  is 
pierced  for  only  one  gun — all  the  other  defences  are  open. 

252... Remake.  The  plan  and  profiles  are  referred  to  a  plane 
of  comparison  taken  -I  feel  below  the  horizontal  plane  of  site. 
The  references  are  in  feet  and  fractional  parts  of  feet.  The 
horizontal  distances  in  yards  and  feet. 

253. ..The  leading  idea  which  seems  to  have  governed  Vau- 
ban  in  the  dispositions  of  his  2d  and  3d  Methods,  was  to  make 
the  interior  enceinte  serve  as  a  general  retrenchment  with 
covered  defences,  which  could  be  brought  into  play  at  the 
moment  when  an  attempt  was  made  to  pass  the  interior  ditch 

W 


FAUBAn's  ninn)  METHOD.  91 

either  by  sap  or  openly.  Besides  this  prominent  feature  of  the 
2d  and  ."-'1  Methods,  they  are  both  great  improvements  on  the 
1st  Method,  in  the  greater  dimensions  given  to  the  counter- 
guards  and  demilunes;  in  the  organization  of  the  latter  Murk 
■frith  a  permanent  though  small  redoubt,  and  in  the  better 
covet  afforded  to  the  masonry  of  the  two  enceintes  and  the 
outworks,  both  from  the  relative  position  and  relief  of  t! 
elements.  This  la>t  purpose)  however,  is  but  partially  effected, 
for  the  interior  enceinte,  which,  owing  to  the  small  thinks 
given  t<>  the  demilune  (which  last  have  but  a  slight  bearing  on 
the  defence,  and,  therefore,  might  have  been  omitted),  and  the 
opening  between  the  tenaille  and  counterguard  flanks  fan 
be  breached  from  a  position  near  the  reentering  place  of  arms, 
and  thus  be  exposed  to  assault  at  the  same  time  that  the  breach 
of  the  counterguard  is  attacked.  Besides  this  defect,  a  great 
part  of  the  scarp  wall  of  this  enceinte  in  rear  of  the  tenaille. 
i.>  exposed  to  the  enemy's  view  over  the  tenaille.  as  the  relief 
of  this  wqrk  has  to  be  so  far  reduced  that  the  tire  of  the  cmin- 
terguard  think  can  be  brought  to  bear  on  the  breach  that  may 
be  made  in  the  face  of  the  opposite  counterguard. 

254...The  stone  towers  are  badly  contrived,  both  for  strength 
and  defence.     The  upper  platform,  surrounded    as  it  is  with  a 
Btone  parapet,  and  having  a  traverse  of  the   same    material   in 
the  centre,  would   be  a  perfect   slaughter-house  under  a  h< 
fire  of  artillery  directed  against  it.    The  arches  of  the  c 
mates  are  inconveniently  placed  for  the  ,.t'  the  guns, 

and.    having  the    exterior   walls   for   one   of  their  abutim 
would  give  way  with  the  destruction  of  these  walls,  and  bring 

down  all  the  superstructure  by  then-  fall. 

t   may  !.<■  observed  that  the  in- 
r  enceinte  and   the  couuterguards  have  the  same  com- 
mand, which  would  be  found   greatly  to  the  disadva 
the  forti  :i  ;i~  the  enemj  has  succeed*  d  in 

"ii  of  the  latt<  r. 
256... The  low  r<  nnterguard  and  the  * 

berm  at  top,  would  subj<  •  oik  to  be  assaulted  by 


'.••_'  BMQN1  'ai.ni.m ;'a    M!  inoi). 

lade  at  points  along  it.-  face  and  flanks  at  the  same  tittie  that 
an  assault  is  made  on  it.-  breach  :  thus  paralyzing  the  action  at 
temporary  retrenchments  thrown  up  within  this  work  to  pro- 
tect the  breach. 

L'."iT...It  was  owing,  probably,  to  these  obvious  defects,  and 
tin-  great  cost  of  the  baehoned  towers,  that  Corrnontaingne, 
who,  in  his  writings,  professes  to  follow  out  the  leading  ideas 
of  Vauban,  selected  the  main  features  of  his  1st  Method 
rather  than  those  of  his  2d  and  .".d,  in  the  bastioned  front 
which  has  received  his  name.  Although  imperfectly  devised, 
both  as  to  plan  and  construction,  the  3d  Method  of  Yauhan 
presents  more  elements  of  resistance  than  Cormontaingne'i 
front;  and.  with  suitable  modifications  of  the  interior  enceinte 
and  the  demilune  to  remedy  the  defects  which  have  been 
pointed  out,  and  by  increasing  the  dimensions  of  the  interior 
enceinte  so  as  to  afford  good-sized  bastions,  with  strong  flank- 
ing dispositions,  it  would  oft'er  far  superior  defensive  means 
than  it  now  possesses. 


CORMONTAINGNE'S    METHOD. 


258.. .Corrnontaingne,  the  immediate  successor  of  Yauhan, 
holds  a  place  only  second  to  this  master  of  the  art  in  the  esti- 
mation 01  the  engineers  of  the  French  school.  Corrnon- 
taingne. who  to  superior  abilities  united  a  wide  range  of 
experience,  both  in  the  construction  and  in  the  attack  of  per- 
manent works,  studied  with  great  care  the  results  of  Yauban's 
immense  labors.  In  working  out  the  front  which  has  received 
his  name,  Corrnontaingne  seems  to  have  applied  himself  rather 
to  remedy  the  defects  noticeable  in  the  methods  of  Vauban, 
than  to  produce  any  radical  change  in  the  combinations  which 


COKMoN  I  AIM.M  l'fl     METHOD. 

had  thus  far  received  the  sanction  of  engineers  generally.  He 
was  thus  led  to  reject  the  1st  and  2d  Methods  of  Vauban  from 
the  defects  which  have  beeri  hotic<  d,  and  also  from  the  in- 
creased cost  of  constructing  the  bastioned  towers',  and  to  take 
the  1st  Method  as  the  basis  of  his  own  changi 

259...Cormontaingne  was  the  first  to  develop  clearly  the  in- 
fluence of  large  demilunes  on  the  progress  of  the  attack,  by 
their  forming  deep  reenterings  between  them  in  front  of  the 
bastion  salients,  and  also  the  increased  strength  gained  by  for- 
tifying on  a  right  line,  or  on  polygons  wkh  a  great  number 
of  sides,  as  in  both  of  tlx  the  fronts  assailed  can  no: 

enveloped  by  the  assailant's  works,  and  the  demilunes  from 
their  salient  position  intercept  the  prolongations  of  the  bastion 
faces,  and  thus  mask  them  from  the  positions  from  which  alone 
an  enfilading  fire  could  be  brought  upon  them.  Besides  tliis, 
Cormontaingne  lays  down  a>  a  principle,  that  no  masonry  shall 
be  exposed  to  th<  distant  batteries  of  ih&  assailant;  and  to 
obtain  this  point  he  has  so  arranged  the  height  of  his  principal 
scarps,  and  the  command  given  to  the  glacis  crest  in  front  of 
them,  that  the  top  of  the  scarp  shall  not  lie  aboVe  the  level  of 
this  crest,  thus  masking  the  entire  scarp-,  by  the  earth  forming 
the  glacis,  from  all  positions  in  advance  of  the  glacis  crest 

Sis  modifications  of  the  plan  and  profile  of  Vanbau's  1st 
Mi  thod,  chiefly  result  from  the  above  m  a  basi 

200.. .Enceinte.    Tin-  modifications  of  Vauban's  tract 
4,  PI.  1.  are  different  in  the  various  works  of  Cormontaing 
hut  the  following  he  indicates  in  his  m<  tnoirs  as  the  most 
feet     T  >r  side  i.^  860  yard.-:  the  perpendicular 

the  face- of  the  1'  of  the  exterior  side;  the  flanks  . 

4'»  yard.-,  and  are  -..  placed  that  the  curtain  shall  he  1  i'm  yai 
this  combination  makes  the  Lines  of  defence  somewhat  l< 
and  the  ha.-'  ewhat  -mailer,  than  in  Vauba  thod. 

261. ..The  dimensions  <>t'  the  enceinte  ditch  ai  rnlated 

h\  Cormontaingn<  earth  sufficient  for  the  em- 

bankmei  ilient,  and  IV 


'.'1  OORMOXTAIM.M  .">    MITIIOD. 

4  yards  wider  opposite  the  tenaille;  this  admits  the  entire  fire 
of  tin-  flanks  to  sweep  the  ditch. 

262...Texaille.  The  tenaille  is  made  with  a  curtain  and 
wings;  a  ditch  LO  yards  wide  being  left  between  It,  the  cur- 
tain and  the  flanks. 

l'i;::...I )i  mil ink.  Corniontaingne  placed  little  value  on 
small  demilunes,  as  they  form  l»ut  slight  and,  therefore,  weak 
reenterings  before  the  bastions,  and,  consequently,  retard  but 
little  the  enemy's  attack  upon  the  bastions;  besides  thi 
small  demilune  covers  but  very  imperfectly  the  shoulder 
angles  of  the  bastions.  To  remedy  these  defects,  his  demilune 
is  so  laid  out  that  the  prolongations  of  the  magistrals  of  its 
faces  will  intersect  the  ba.-tioii  faces  at  80  yards  from  the 
Bhoulder  angles;  the  lengths  of  its  faces  being  L30  yards. 

•j<;4...By  thus  enlarging  the  demilune,  sufficient  space  is 
gained  to  place  a  strong  redoubt  in  its  interior.  The  defence 
of  the  demilune  may  be  made  with  more  obstinacy,  from  the 
Bupport  it  receives  from  the  redoubt;  and  the  enemy  will  be 
obliged  to  carry  the  redoubt  before  he  can  assaull  the  in-each 
lie  may  have  made  in  the  bastion  face,  as  this  breach  is  see* 
in  reverse  by  the  fire  of  the  flanks  of  the  redoubt. 

£65. ..Demilune  Reduit.  To  circumscribe  as  much  as  prac- 
ticable the  space  in  the  demilune  which  the  enemy,  after  he 
gains  it,  requires  for  his  works,  the  extremity  of  the  demilune 
terreplein,  which  is  also  the  top  of  the  counterscarp  of  the,  re- 
doubt, is  drawn  at  20  yards  from  the  magistral  of  the  face; 
tin'  ditch  qf  the  reddidit  is  10  yards  wide,  and  the  magistral 
of  its  face  is  parallel  with  the  counterscarp.  By  this  arrange- 
ment the  ditch  of  the  redoubl  is  well  flanked  by  the  face  of 
the  bastion  near  the  shoulder  angle.  To  lay  out  the  Hanks  of 
the  redoubt,  the  counterscarps  of  the  enceinte  are  prolonged 
to  intersect  the  perpendicular  of  the  front;  from  this  point  of 
intersection  a  distance  of  20  yards  is  set  oil'  along  each  coun- 
terscarp, the  two  points  thus  obtained  arc  joined  by  a  right 
line,  which  is  the  gorge  of  the  redoubt;  from  the  extremities 
of  the  gorge  two  lines  are  drawn  parallel  to  the  capital  of  the 


cormontaim.xk's  method.  95 

demilune,  those  linos  limit  the  torreploin  of  Ihc  flanks;  the 
magistrals  of  the  flanks  arc  drawn  parallel  to  and  at  in'  yards 
from  the  last  lines.  The  ditch  of  the  demilune  is  20  yards 
wide;  its  depth  is  the  same  as  that  of  the  enceinte. 

2(J6...Cov]  Ri  o-way,  bto.  The  general  width  of  the  eovered- 
way1  is  10  yards.  Cormontaingue  enlarged  considerably  the 
reentering  place  of  arms,  to  which  he  added  a  redoubt  with  a 
revetted  scarp  and  counterscarp.  The  addition  of  this  redoubt 
la  a  great  improvement  upon  the  covered-way  of  Vauban,  who 
indicates  in  his  works  small  redoubts  of  earth,  or  tambours  of 
wood,  for  the  same  purpose.  Cormontaingne'a  redoubt  in- 
creases the  Btrength  of  the  covered-wayj  the  troopd  assembled 
in  the  covered-way,  for  sorties,  are  Becure  under  its  fires:  it 
6oos  in  reverse,  and  protects  any  breach  made  in  the  face  of 
the  demilune;  finally,  it  serves,  in  connection  with  the  ex- 
tremity of  the  demilune,  to  cover  the  opening  left  between  the 
flank.-  of  tlie  baatioe  and  the  wings  of  the  teuaille,  through 
which,  if  a  breach  was  made  in  the  curtain,  the  interior  re- 
trenchments, resting  upon  either  the  flanks  or  face.-  of  the  bas- 
tion, could  he  turned. 

•J|>7...To  lay  out  the  interior  crests  of  the  reentering  place  of 
urns,  two  points  .-ire  taken  on  the  counterscarps  of  the  bastion 
and  demilune,  at   54  yards  from  their  point  of  intersection; 

from  these  point-  a-  c  Qtres,  with    radii    of   60   yard-,  arcs   are 

ribed,  whose  in*  ,  joined   with  the  centn 

the  direction  of  the  face-.     The  magistral  of  it>  redoul  I 
found  by  a  similar  construction j  distances  of  J"  yards  being 
off  along  the  counterscarps,  and  the  faces  being  drawn 
from  these  point-  bo  :i-  to  be  86  yards  long.    The  ditch  of  the 
redoubt  i.-  5  yards  wide  and  2\  yards  deep. 

268„.Tj  are  placed  along  the  covered-way,- to  d 

the  places  of  arms,  defend  th<  i-way.  and  intercept  pro- 

fircd  in  ri 
269...The  i 
line,  to  allow  room  iW  th<  -  of  the  •  ' I " I n •  short 

bran  throw  a  lire  on  the  salient 


96  i:M"M  \in.;\i.">   mi :i  hod. 

covered-way;  ihe  positions  of  the  long  branches  are  bo  taken 
that  the  defiles  may  be  seen  and  Bwept  by  the  liiv  of  the 
works  in  their  rear, 

270... Profiles.  Cormontaingne,  after  a  series  of  trials,  whose 
•t  was  to  give  the  ditohes  such  dimensions  that  they  should 
I'lirn  i>li  the  earth  required  for  the  embankments,  regulated  the 
command  of  the  different  works  as  follows:  The  lowest  work, 
which  is  the  demilune  covered-way,  he  lavs  down  as  a  rule, 
shall  command  the  exterior  ground  by  not  less  than  7  A  feel  ; 
and  the  works  most  advanced  shall  be  commanded  by  those 
in  their  rear. 

■_'7l... It  was  found  that,  for  the  purpose  of  equalising  the 
excavations  ami  embankments  of  tin-  front,  the  crest  of  the 
demilune  covered-Way  should  have  a  command  of  1<»A  feet 
above  the  natural  ground.  The  crest  of  the  bastion  covered-; 
way,  ami  of  the  reentering  place  of  arms,  command  the  crest 
of  the  demilune  covered-way  by  2  feet.  The  magistral  of  the 
enceinte  is  horizontal,  its  elevation  being  the  same  as  the 
mean  elevation  of  the  crest  of  the  bastion  covered-way.  The 
salient  of  the  bastion  commands  its  covered-way  by  8  feet 
The  total  height  of  the  scarp  is  30  feet.  This  dimension  has 
since  been  generally  adopted  by  engineers— a  wall  of  this 
height  opposing  a  sufficient  obstacle  to  an  attempt  at  escalade, 
The  absolute  relief  of  the  flanks  is  thus  made  37-J   feet ;  with 

this  relief  a  piece,  firing  under  a  depression  of  l-(>  through  an 
embrasure  in  the  Hank,  and  in  the  direction  of  the  curtain, 
will  strike  the  bottom  of  the  ditch  at  the  middle  point  of  the 
Curtain;  BO  that  were  the  relief  increased,  the  length  of  cur- 
lain  remaining  the  same,  the  ditch  would  no  longer  be  thor- 
oughly flanked. 

272..,Thfl  relief  of  the  tenaille  is  determined  as  in  Yauban's 
Method,  so  as  not  to  mask  the  lire  of  the  flanks  upon  the  ditch 
opposite  the  extremity  of  the  demilune,  as  it  is  here  that  a 
breach  may  be  made  in  the  bastion  i'aee  through  the  ditch  of 
the  demilune. 

273...The  demilune  is  commanded  by  the  enceinte,  3  feet, 


COKMo.NTAIM.NkV    Ml   I'lIOD.  !»7 

and  by  its  own  redoubt,  H  feel ;  the  demilune,  therefore,  com- 
mands its  covered-way,  7  feet,  which  is  more  than  La  indispens- 
ably requisite;  for  ;m  enemy,  standing  on  the  crest  of  the 
covered-way")  cannot  hare  a  plunging  fire  into  a  work  in  the 
rear  of  it  it'  the  latter  commands  the  cresl  by  5  feet. 

274..,The  redoubt  of  the  reentering  olace  of  arms  commands 
the  crest  of  the  glacis  only  4$  feet;  its  interior  caesl 
placed    as   not  to  mask   the  tire  of  the  bastion   faces  on   the 
glacis  in  advance  of  it. 

875... Hie  interior  crests  of  all  the  works  are  7£  feet  above 
their  terreplein,  except  that  of  the  tenaille,  which  is  *»-£ 
feet,  and  of  the  redoubt  oftlie  reentering  placeof  arms,  which 
i.-  !'  feet.  The  interior  crests  of  the  faces  of  all  the  work- 
posed  t<»  enfilading  tires  are  one  foot  higher  at  the  salients 
than  at  the  extremities. 

27n\..The  profile  of  the  parapet  of  the  principal  outwork 
-.line  as  that  of  the  enceinte. 

L'77...(.'oMMt-.\-i<  \iio\>.  The  communications  are  generally 
of  the  same  nature,  and  placed  about  in  the  same  positions,  as 
in  Vanban'fl  Method. 

l'7v...<.]  u  i-.  The  planes  of  the  glacis  are  bo  determined 
that  they  may  be  swept  by  the  lire  of  the  works  in  the  rear  : 
their  inclination  is  usually  about  twenty-four  base  to  one  alti- 
tude. 

879...Interioh    Retbenobxentb.     Oormontsingne   indict 

the  gorge  and    ghouldeN  of  the    ha-thm  as  the  position    for  an 

interim- retrenchment,  when  this  addition   to  the  front  is  made 
solely  with  a  view  of  disputing  the   breach  in   the  bastion  and 
its  interior  with  the  assailant.      In   this  CM 
treiichment  the  form  of  a  tenaille.  or  a  bastioned  front, 

her  upon  the  shoulder  angles  of  the  bastion,  or  npon  the 

two  adjacent    curtain.-,  on    points   beyond    the    pro 

ditch  between  the  tenaiiles and  the  flanks, and  in  tl 
it  tin-  form  d  front. 

In  the  form  .  the  port 

nee,  but    • 
13 


:|V  <  OBMOCT  Ai.Ni.M  ;'a    Million. 

trenchment  is  liable  to  be  turned,  by  a  breach  made  in  the 
Hank.  <.r  in  the  portion  of  the  curtain  where  it  joins  the  flank. 
In  the  latter  ease,  a  breach  in  the  bastion  places  the  whole  of 
the  interior  within  view  of  the  assailant,  bnt  the  retrenchment 
itself  is  secure  from  its  position  from  being  turned,  as  a  breach 
in  tin-  curtain  cannot  In-  made  in  rear  <>t'  it. 

280.. .<  \\  .\ i  ii BR,  When  a  greater  command  of  the  site  than 
that  afforded  by  the  enceinte  is  requisite  on  any  front.  Cor- 
montaingne  places  a  cavalier  within  the  bastion.  To  this  work 
he  gives  the  same  form  ;is  thai  of  the  bastion,  placing  the  faces 
ami  flanks  of  the  two  parallel  to  each  other.  The  faces  of  the 
cavalier  arc  alone  revetted,  as  well  as  the  counterscarp  of 
their  ditch  which  is  cut  within  the  bastion.  This  ditch  is 
broken  off  at  the  shoulder  angles  <>t  the  cavalier  ami  directed 
upon  the  faces,  these  portions  also  bavin--  a  revetted  scarp  and 
counterscarp.  A  parapet  is  thrown  up  behind  the  scarp  and 
between  the  flank  of  the  cavalier  and  the  bastion  faces,  thus 
isolating  the  anterior  portion  of  the  bastion,  and  furnishing  an 
interior  retrenchment  which,  when  the  shoulders  and  flanks  of 
the  bastions  are  masked  from  the  assailant's  view,  can  only  be 
carried  by  a  breach  made  either  in  the  cavalier  face  or  in  the 
portions  resting  on  the  cavalier  and  bastion  faces. 

•  281...Kkmai;ks.  From  the  preceding  description,  it  appears 
that  the  most  important  modification  made  by  Cormontaingne, 
in  Vauban's  1st  Method,  consists  in  the  means  taken  to  cover 
the  masonnj  from  distant,  batteries;  capacious  bastions,  sus- 
ceptible of  receiving  efficient  permanent  interior  retrench- 
ments; an  enlarged  demilune,  which  places  the  bastions  in 
strong  refinterings,  covers  the  shoulder  angles,  and  admits  of 
a  redoubt  in  its  interior,  which  work  strengthens  the  demilune, 
and  sees  in  reverse  the  breach  made  in  the  bastion  face;  an 
enlarged  reentering  place  of  arms,  containing  a  redoubt,  which 
strengthens  the  entire  covered-way,  and  covers  the  movement 
of  the  troops  in  sorties. 

282.. .These  modifications,  although  of  great  value,  and  con- 
stituting an   important  step  in  the  art,  still  leave  much  to  be 


M 


METHODS    OF    THE    SCHOOLS  OF    M  K/.IKKKs    WD    METZ.  99 

desired ;  and  engineers,  since  Cormontaingne's  time,  have 
BOtlght  to  remedy  the  detects  of  his  method,  of  which  the  fol- 
lowing  arc  the  principal.  The  enceinte  lias  rather  too  slight 
a  command,  and  it  is  without  any  bomb-proof  shelters ;  the 
inclination  of  the  superior  slope  of  its  parapet,  which  is  1-9, 
is  too  small  to  have  the  ditches  well  flanked  ;  a  breach  can  be 
made  in  the  bastion  face  through  the  ditch  of  the  demilune; 
there  are  dead  spaces  in  the  ditch  of  the  demilune  near 
the  extremities  of  its  faces;  the  redoubt  of  the  reentering 
place  of  arms  is  not  tenable  after  the  demilune  is  taken  ;  the 
traverses  of  the  covered-way  do  not  afford  the  requisite  pro- 
tection to  thai  work  ;  finally,  communications  are  mostly  in- 
convenient, and  not  well  covered  from  the  assailant's  fires. 


METHODS  OF  THE  SCHOOLS  OF  .1IEZIERES  AND  METZ. 


L'v."....The  School  of  Application  tor  engineer  and  artillery 
officers,  first  established  at  tfezieres-and  subsequently  at  M<u. 
has  given  to  France,  from  about  the  period  of  the  French 
R  volution  down  to  the  presenl  day,  the  far  greater  portion  of 
the  many  able  officen  who  have  gained  such  universal  and 
red  celebrity  for  these  two  corps. 

L'M...In  these  schools  the  precept!  of  Vauban  and  Cormon- 
taingne  have  been  jealously  guarded  ;Js  the  highest  authority, 
and  their  manuscript*  and  published  works  have  formed  the 
of  the  instruction  given  in  them. 

2s.     -  lit  modifications  were  proposed  in   theft 

of  Cormontaingne  by  two  ' 


100        METHODS  OF   THE   SCHOOLS    OF   MUlflUS    \M>   MKTZ. 

and  taught  by  them  in  the  course  of  permanent  fortification 
given  in  the  school.  These  changes  chiefly  consisted  in  en- 
larging the  demilune  and  making  it  more  ,-alient;  and  in 
placing  in  the  flanks  of  its  redonbl  casemates  for  cannon,  with 
reverse  views  on  the  breaches  that  might  be  made  in  the  bas- 
tion faces. 

280...The  teaching  of  tlu-  Bchool  of  Met/.  has  received  its 
principal  impress  from  Genera]  Noizet,  himself  a  pupil  of 
General  Bazo,  regarded  as  the  first  among  the  successors  of 
Vauban  and  Oormontaingne,  who,  for  several  years,  whilst  si 
captain  <»t'  engineers,  performed  the  functions  of  professor  of 
fortification,  and  who  has  recently  given  to  the  public  the  re- 
sults of  his  lectures  delivered  in  the  school. 

28T...The  front,  which  for  sonic  years  hack  and  up  to  the 
present  time,  has  been  taught  in  this  school,  goes  by  the  ap- 
pellation of  Xoizi  /'.*  Mi  thod.  In  it  there  is  no  sensible  depar- 
ture from  the  views  and  methods  of  Vauban  and  Oormon- 
taingne; the  object  being  to  introduce  such  modifications  into 
the  front  of  the  latter  as  would  remedy  some  of  its  acknowl- 
edged defects.  In  doing  this,  another  object  was  kept  in  view, 
which  was  to  present  in  the  combinations  of  this  front  a  prob- 
lem, in  the  solution  of  which  the  pupil  would  be  called  upon 
to  apply  both  the  elementary  principles  of  fortification  and  the 
geometrical  methods  that  the  engineer  has  to  use  as  his  princi- 
pal tool  in  such  problems  to  a  special  case,  that  oi  a  front 
adopted  to  a  horiecntai  aitd.  It  is  in  this  point  of  view  that 
the  analysis  and  construction  of  this  i'ront  have  been  adopted 
as  the  basis  for  the  elementary  instruction  given  in  permanent 
fortification  in  this  institution. 


ntoizet's  method.  101 


NOIZET'S    METHOD. 


288... General  Ki  quibbmebts.  Noizet,  in  his  front,  takes  as 
the  basis  of  the  construction  of  the  enceinte,  the  length  of  the 
exterior  Bide  and  the  command;  assuming  these  within  the 
limits  laid  down  by  Yauban  and  Cormontaingne;  and  in  the 
combinations  of  outworks  with  the  enceinte,  following  the 
latter  engineer;  introducing  only  Buch  modifications  as  seem 
t<>  beet  fulfill  the  general  conditions  of  the  problem,. which  are 
as  follows: 

1st.  The  enceinte  must  be  secure  from  a  surprise  by  esca- 
lade: present  an  unbroken  line  on  every  side  by  which  it 
can  be  approached  by  the  assailant;  and  hare  its  scarp  tho- 
roughly swept  by  fire  from  within  the  enceinte. 

I'd.  The  parapets  of  the  enceinte  and  outworks  must  be 
proof  against  projectiles  <»f  the  heaviest  calibre. 

I'd.  The  scarp  walls  of  the  enceinte  and    outworks  must   be 

masked  from  all  positions  that  can  be  taken  up  by  the  assail- 
ant for  bis  breaching  batteries  beyond  the  crt  st  of  the  gls 

4th.  The  flanking  dispositions,  both  of  the  enceinte  and  out- 
work.-, must  be  adapted  bo  the  range  of  small  arm.-,  within 
irate  lira 

i.  The  command  of  the  enceinte  must  be  so  regulated  as 
i  erlook   all   the   outworks  and  bring  their  interior,  their 
ditches,  the  glacis  and  the  site  beyond  it  thoroughly  under  lire 
of  both  artillery  and  BtnaU  ai 

i        command  of  the  outwork-  must  1"'  so  combii 
that  the  more  adi  shall  be  commanded  by  the  i 

tired;    and,  when  this  cannot  1  d,  the  retii 

which   is   commanded    by    an   advai 
int< 


103  roust's  ig  raoft 

7th.  The  outworks  must  be  so  combined  that  they  shall  tall 
into  the  possession  of  the  assailant  in  succession,  from  the 
more  advanced  to  the  more  retired;  and  the  more  important 
ones  should  receive  a  sufficient  height  of  scarp  wall  to  secure 
them  from  being  entered  by  a  sudden  rush  of  the  enemy. 

Bth.  There  must  be  a  sufficiency  of  tin'  various  kinds  of 
communications  to  admit  of  a  prompt  circulation,  both  within 
the  enceinte  ami  to  the  exterior,  tor  the  ordinary  service  of 
the  garrison  and  for  sorties  against  the  assailant. 

28!»...<ii  m  SAL  Data  OF  THE  Km  i  intk.  In  the  following  de- 
scription ami  analysis  of  the  front  of  Noizet,  the  plane  of  com-i 
parison  is  assumed  at  60  tot  below  the  horizontal  plane  of 
.  the  reference  of  which  will  he,  therefore,  (60,0).  The 
yard  is  taken  as  the  unit  for  the  horizontal  dimensions  of  the 
plan  ;  and  the  foot  as  the  unit  for  the  references  and  vertical 
dimensions. 

Converting  the  French  measures  into  their  equivalent  Eng- 
lish units,  the  exterior  side  of  the  front  is  880  yards;  the 
height  of  the  scarp  wall,  .'>.">  feet ;  the  command  of  the  interior 
Crest  of  the  curtain  over  the  plane  of  site,  L'l  feet;  and  its 
height  above  the  magistral,  13  feet. 

29<i...Pkoj  ii. k  of  Enceinte.  PI.  2,  Fig.  4.  The  profile  of 
the  enceinte  here  given  is  similar  to  that  of  Oofmontaingne, 
and  was  adopted  by  subsequent  engineers  until  the  more  re- 
cently modified  one  already  described.  Its  slopes  and  dimen- 
sions are  as  follows:  The  scarp  and  counterscarp  slopes,  20-1, 
or  one  base  to  twenty  altitude.  Exterior  slope,  1-1,  or  15°. 
Superior  slope,  l-G.  Interior  slope,  3-1.  Banquette-slope,  4. 
Rampart-slope,  $.  Terreplcins  S  feet  helow  the  interior  crests. 
I'.erin,  2  feet.  Distance  between  the  magistral  and  foot  of  the 
exterior  slope,  L.5  feet.  Thickness  of  parapet,  20  feet  Height 
of  interior  crest  above  the  banquette-tread,  4.5  feet.  Ban- 
quette-tread, K.">  feci.  General  width  of  terreplein,  estimated 
from  the  vertical  through  the  interior  crest,  48  feet. 

2DJ...M  ai.i.vi  Bill  OF  iin:  (Vktain.  The  length  of  this  is 
determined  by  the  condition  that  the  artillery  fire  from  the 


\ot/.i.t"s  mkthod.  103 

.flanks,  under  the  depression  of  1-fi,  shall  attain  a  point  at  1.5 
feet  above  the  bottom  of  the  ditch,  at  tin-  centre  of  the  cur- 
tain ;  the  bottom  of  the  ditch  itself,  at  the  centre,  being,  for 
r the  purposes  of  drainage,  L. 5  feet  higher  than  at  the  extremi- 
ties of  the  curtain,  thus  giving  to  the  scarp  a  height  of  31.50 
feet  at  the  centre,  instead  of  33  feet,  the  general  height 
throughout  the  enceinte. 

Supposing,  now.  a  section,  PI.  -.  Figs.  2,  4,  to  be  made 
through  the  flanks  by  a  vertical  plane  passed  through  the  foot  of 
the  curtain  scarp,  and  that  a  line  he  drawn  in  it,  parallel  to  the 
superior  slope  and  at  3  feet  below  it,  to  represent  the  direction 
of  the  artillery  tire,  this  line  must  attain  the  point  at  1.5  feet 
above  the  bottom  of  the  ditch,  at  the  centre  of  the  curtain,  to 
fulfill  the  required  condition  of  a  thorough  flanking  disposition 
throughout  the  entire  extent  of  the  enceinte.  If,  then,  a  hori- 
zontal line  he  drawn  from  the  point  to  lie  attained  to  intei 
the  vertical  through  the  interior  crest,  it  will  be  the  horizontal 
distance  between  the  interior  crest  and  the  centre  of  the  cur- 
tain, and  from  the  construction,  will  he  equal  to  six  times  the 
perpendicular  distance  intercepted  between  it  and  the  line  of 
artillery  fire.  f 

Now.  from  the  above  there  i-  given  to  calculate  this  hase 
the  entire  height  of  the  interior  crest,  above  the  bottom  of 
the  ditch.  44.60  feet :  the  height  of  the  same  point  above  the 
line  of  artillery  I  t  ;  and   the  height  of  the  point  to  he 

attained  above  the  bottom  of  the  ditch,  L. 5 feet.     The  distance 
•OUght,  then), -re.  will    he  .;   H.:,o  ft. — UK)  ft.,-l'4M  ft. 

To  obtain  the  length  of  the  magistral  corresponding  to  this 
distance,  it  will  only  be  requi  abtract  from  it  the  hori- 

zontal distance  between  the  interior  crest  and  the  point  ot 
on  corresponding  to  the  magistral  ot  the  flank.     Thia 
distance  is  composed  of  the  thick'  the  parapet,  the  1 

of  the  exterior  slope,  and  the  herm.     The  first  i-  20  feet. 

id  is  found  by  taking  from  the  height  of  theii 
above  the  mag  stral,  which  is   13  tb  the  thick' 

of  the  para] 


Ill4  N"l/.l   l"">     Ml   1  HOD. 

feet.     The  third  is  1.50  feet.    The  required  distance;  therefore*,. 

!,,  ft.— il'.i  i't.  +  O.OG  ft.+1.50  ft.)  =  20S.S4  feet,    or  00.(11 
yards. 

292...Magisteal  of  Km mmi:.  PL 2, Fig.  5.  Having  found* 
the  Length  of  the  magistral  of  the  curtain,  the  projection  of 
the-  magistral  of  the  enceinte  on  the  plane  of  reference  is  de- 
termined as  follows:  Draw  aline  for  the  exterior  Bide,  and  Bel 
off  on  it  .1  II  :380  yards ;  bisect  this  distance  by  a  perpen- 
dicular, on  which  set  oif  C  IJ=l-6  A£=63.33  yards;  from  A 
and  B  draw  lines  through  D,  these  are  the  directions  of  the 
laces  and  lines  of  defence ;  draw  a  parallel  to  0  D,  on  each 
Bide  of  it.  and  at  69.61  yards,  the  length  of  the  half  curtain,  from 
it,  join  tin'  points  0  and  //  where  these  parallels  intersect  the 
lines  A. D  and  B  I)  prolonged;  G  II  is  the  position  of  the 
curtain;  G  IJ  and  II A  the  lines  of  defence;  from  0  and  // 
draw  a  line,  making  an  angle  1-6  with  the  perpendicular,  to 
the  curtain  at  each  of  these  points;  the  parts  0  /'/and  F II  oi 
these  last  lines  are  the  thinks,  and  .L  /'.'and   B  /-'the  faces. 

293. ..The  position  of  the  magistral  with  respect  t<»  the  plane 
of  reference,  is  determined  as  follows:  The  magistral  of  the  cur- 
tain is  horizontal.  As  it  is  13  feet  below  the  interior  erestj 
and  this  line  is  placed  at  '21  feet  above  the  plane  of  site,  the 
magistral  is  8  feet  above  this  plane,  and,  therefore,  from  the 
position  given  the  plane  of  comparison,  6S  feet  above  this  last. 
plane;  its  reference,  therefore,  is  (68.0).  The  flank  is  1.5  feet 
lower  at  the  shoulder  than  at  the  curtain  angle,  the  reference 
of  the  shoulder  is.  then,  (66.50).  Tho  face  is  horizontal,  and 
its  reference  also  (66.50). 

294.. .M  anm:u  OF  iil.'i'llJ.MlM.No  nil'.  POSITION  OF  A  POINT  OF  mi. 
Interiob  C$S6T,  To  determine  the  projection  of  a  point  of 
the  interior  crest  contained  in  a  profile  plane,  the  height  of 
the  point  above  the  magistral  being  known,  we  first  subtract 
from  this  height  1-6  the  thickness  of  the  parapet,  the  remainder 
will  be  the  height  of  the  exterior  crest  above  the  magistral, 
and,  when  the  exterior  slope  is  1-1,  will  also  be  the  base  of 
the  slope;  adding  together  the  thickness  of  the  parapet,  the 


noizkt's  method.  105 

base  of  the  exterior  slope  as  just  determined,  and  the  distance 
from  the  foot  of  -  the  exterior  slope  to  the  magistral,  the  sum 
will  be  the  horizontal  distance  between  the  magistral  and  inte- 
rior crest,  or  the  distance  to  l>e  set  off,  along  the  trace  of  the 
profile  plane,  from  the  magistral,  to  obtain  the  projection  of 
the  required  point  of  the  interior  crest. 

L'!C>...Ixtki;toi;  CbEST  Off  THE  Knminii.  PI.  2,  Fife  H.  The 
position  of  the  interior  crest  above  the  magistral  is  fixed  as 
follows:  That  of  the  curtain  is  parallel  to  the  magistral,  and 
13  feet  above  it.«  Those  of  the  flanks  ami  faces  of  the  bastion 
an'  contained  in  the  same  plane,  the  scale  of  declivity  of  which 
is  taken  parallel  to  the  bastion  capital.  The  position  of  this 
plane  is  determined  by  placing  its  horizontal,  which  coincides 
with  a  pancoupe*  4..">u  yards  in  length  at  the  bastion  salient,  at 

4..*><>  feet  above  the  horizontal  drawn  through  the  points  where 
the  flanks  join  the  curtain. 

The  reference  of  the  interior  crest  of  the  curtain  from  the 
above  data  will,  therefore,  be  ('Sl.(i);  and  the  horizontal  dis- 
tance .,t'  any  point  of  it  from  the  magistral  31.16  feet,  or  10.38 
yards,  as  these  two  lines  are  parallel* 

Having  drawn  the  projection  of  the  interior  crest  of  the 
curtain,  the  point  where  it  joins  the  flank  may  be  determined 
approximately,  and  with  sufficient  accuracy,  by  bisecting  the 
curtain  angle  of  the  magistrals,  and  taking  the  point,  wl 
the  bisecting  line  cuts  the  interior  civ-t.  as  the  extremity  of 
the  flank.  From  this  point,  of  which  the  ref 
if  a  line  be  drawn  perpendicular  to  the  bastion  capital  it  will 
be  horizontal  (81.0)  of  the  plane1  of  the  interior  a  the 

ion  :  that  at  the  pancoupe  is  4..*.<>  feel  higher,  and  rta  n 
will,  therefore.  I  To  find   the  position   of  this 

\uH  horizontal,  which    is   also  that  of  the  pancoupe,  draw  ' 
lines  parallel  to  the  bastion  capital,  and  2.16  yards  from   it, 
they  will  limit  the  pancoupe'.     Now,  a-  the  extremity  of  tin-. 
pancoupe*  i-  a  point  ..;  i1.''  i  of  the  bastion  fa 

and  it.-  n  te  h<  ighl  of  this  pou 

stral  i>  1'.'  feet,  as  tin 
14 


106  vizi.rV   KKHOD. 

The  horizontal  distance,  therefore,  from  this  point  to  the  mag- 
istral is  (90  ft. +15.66  ft.  +1^50  l't.)  =  37.1(>  ft. =12.36  yard* 
Drawing  a  parallel,  therefore, "to  the  magistral  of  the  face,  ami 
at  L2.38  yards  from  it,  the  point  where  it  cuts  the  parallel  to 
the  Capital,  a1  2.15  yards  from  it,  will  be  the  required  point, 
tihrough  which  the  horijontal  (85.50)  is  drawn. 

I  laving  tw<-  horizontals  of  the  plane,  its  Bcale  of  declivity  can 
be  constructed,  and  other  horizontals  be  detertnined.  The  pro- 
jection of  the  poinl  of  the  interior  crest  of  the  face  on  any  givea 
horizontal,  can  lie  found  by  the  same  process  as  the  one  jiist 
described,  For  example,  take  the  horizontal,  (84.0)  5  the  per- 
pendicnlar  distance  of  the  point  on  it  from  the  magistral  i>  (90 
ft.+l4.16  ft.-f  !.:.<)  ft.)=35.06  ft.  or  11.88  yds.  The  two  points 
thus  determined  being  joined,  will  give  the  projection  of  the 
interior  crest  of  the  face. 

To  find  that  of  the  flank,  of  which  one  point,  (81.0),  lias  been 
found,  bisect  the  shoulder  angle  of  the  magistral,  the  point 
where  the  bisecting  line  cuts  the  interior  crest  of  the  face  will 
give,  approximately,  the  other  extremity  of  the  line  required* 

The  constructions  for  the  interior  crests,  just  given,  are  only 
approximations  to  a  true  result  ;  as  the  horizontal  distances 
calculated,  being  those  contained  in  profile  planes,  ought  to 
have  been  set  oft*  perpendicular  to  the  projection  of  the  interior 
crest;  but  the  difference  between  the  results  of  this  approxi- 
mate method  and  one  rigorously  accurate  will,  in  the  present 
case,  be  so  small,  owing  to  the  slight  divergence  between  the 
projections  of  the  magistral  and  interior  crest  of  tin- face,  as 
not  to  affect,  in  any  appreciable  degree,  the  real  positions  of 
the  required  points.  The  same  remarks  are  applicable  to  the 
constructions  for  finding  the  extremities  of  the  flank. 

29C...1\\kai,kt  ok  En<  i.inii:.  Having  drawn  the  interior 
crest  of  the  enceinte,  all  the  other  lines  of  the  parapet — except 
the  foot  of  the  exterior  slope. — and  the  inward  line  of  the  terre- 
ph'in  are  drawn  parallel  to  it.  The  foot  of  the  exterior  slope 
is  drawn  parallel  to  the  magistral. 

Tikkki-i.i.ix  of  Kxei.iMi.     PL  2,  Fig.  (i.     The  tcrrcpleins  of 


noi/i :r's   MKTiion.  107 

the  faces  and  flanks  are  in  a  plane  parallel  to  that  of  their  in- 
terior crest  and  8  feet  below  it.  estimated  vertically.  To  find 
the  reference  of  any  horizontal  of  the  terreplein,  it  will  be  only 
necessary  to  subtract  8  feet  from  the  corresponding  one  of  the 
Interior  crests.  Tims,  (85.50)  being  ■  reference  of  a  horizontal 
of  the  interior  crest,  that  of  the  terreplein  corresponding  is 
(77.:»0). 

The  terreplein  of  the  curtain  slopes  1  foot  from  the  foot  of 
tin-  banquette-slope  to  its  inward  line,  which  places  this  last 
line  9  feet  below  the  interior  crest. 

297...Kami'.\i.i-m.mi-i;  and  Ramps.  PI.  2,  Fig.  6.  The  ram- 
part-slopes are  planes  of$-,  passed  through  the  inward  lines  of 
the  terrepleins.  The  lines  of  intersection  of  the  rampart-slopes 
and  plane  of  site  are  found  in  the  usual  way. 

The  ramps  Leading  from  the  plane  of  site  to  the  terreplein 
Ive  an  inclination  of  L-9,  and   they  are  4.30  yards  wide 
Two  of  them  arc  placed  on  the  enrtain,  one  on   the  flank,  and 
one  on  the  face. 

B98...AxALYsn  o*  <  kwrsTBi « ifom  ldovw  d  bob  mi  K\<  i  in  n. 
et,  in  the  plan  of  his  enceinte  has  adopted  dimensions  and 
constructions  which  give  results,  for  the  most  part,  the  same 
M  those  of  Vanhan  and  Oormontaingne,  making  the  defei  - 
properties  of  these  different  methods  about  eqaaL  Tlie  extent 
of  the  exterior  side,  the  length  of  the  curtain,  the  diminished 
angle,  and  the  dii  ned  for  the  flanks,  produce  a  com- 

bination by  which  an  efficient  flanking,  both  as  to  direction  and 
amount  of  lire,  for  the  entire  scarp,  and  ■  powerful  c 
upon  tie  l-way  and  its  glacis  in  advance  of  the  bastion 

nt.     The  lines  of  defence,  by  this  combination,  being  with- 
in the  effective  range  of  small  arms,  and  the  flaaka  capabli 

iving  a  battery  superior  to  the  counter-battery  that  can  bis 
bronght  against  them  from  the  glacis  crest  of  the  oppo 
end-way. 

•'...The    dimensions    and    form    of    the    profile    are    those 
usually  adopted  for  perman<  at  works,  where  the  embankn* 


l^s  n..i/.i:t's   METHOD. 

arc  formed  of  ordinary  earth,  and  the  revetement  walls  of 
good  masonry. 

They  are  Mich  ae  experience  baa  shown  will  give  durability 
and  stability  to  the  masonry,  from  the  pressure  of  the  embank- 
ments and  tin'  ordinary  causes  of  destructibility  to  which  it  Is' 
liable  when  exposed  to  the  weather;  and  to  the  ramparl  and 
parapet  the  strength  to  resist  the  action  of  the  heaviest  artil- 
lery; whilst  they  offer  to  the  assailed  every  convenience  for 
their  prompt  action  and  the  ase  of  their  anus. 

300...The  width  and  Blopes  of  the  ramps  are  regulated  for 
the  passage  of  artillery.  Where  the  height  to  be  overcome  is 
slight,  as  that  between  the  terreplein  and  barbette,  the  Blope 
of  the  ramp  may  be  as  great  as  L-6,  ami  it>  width  be  3.30  yards. 
"Where  the  height  is  greater,  the  declivity  of  the  ramp  should 
be  proportionally  less  steep,  ami  its  width  be  4.30  yards  at 
Least. 

301. ..The  position  of  the  terreplein  with  respect  to  the  in- 
terior crests,  is  that  usually  considered  necessary  t<>  give 
shelter  to  the  troops  ami  materiel  on  it.     By  inclining  that  of 

the  bastion,  the  materiel  and  /><  rsOflfti  1  on  the  faces  and  thinks 

are  better  covered  from  the  enfilading  and  ricochet  lire  than 
they  would  Ik-  if  tin-  terreplein  was  horizontal;  as  a  hall  pass- 
ing Over  the  salient  will  reach  an  inclined  terreplein  at  a  point 
farther  fro^i  the  salient  than  one  which  is  horizontal.  The 
height,  l..~."  feet,  at  which  the  salient  is  placed  ahove  the  cur- 
tain, is  as  great  as  can  he  admitted  in  a  hexagon,  the  Least 
polygon  to  which  the  tract'-  adopted  is  applicable;  because,  if 
placed  higher,  the  plane  of  the  interior  crest  of  the  bastion, 
prolonged  hack,  would  intersect  the  plane  of  site  in  a  line 
Which  would  fall  without  the  salients  of  the  two  adjacent  has- 
tens <.f  the  polygon,  and  these  bastions  would,  therefore,  not 
!•  the  one  between  them  from  reverse  lire 
The  Blopes,  moreover,  of  the  terrepleina  keep  them  in  a  ser- 
viceahle  Mate,  by  not   allowing  the  rain-water  to   collect  and 

remain  upon  them. 
802...Pabticttlab  Conditions  ok  the  Outwoeks.    The  out- 


N0IZ1  l\s    M1TFIOD.  109 

works,  besides  satisfying  the  general  conditions  already  laid 
down,  are  connected  with  each  other  by  several  minor  relations 
of  defence  and  suitableness,  growing  out  of  their  relative  | 
tions,  which  give  rise  to  many  seemingly  arbitrary  construc- 
tions and  details  for  each  one.  ilie  bearing  of  which  cannot  be 
clearly  explained  until  a  description  of  the  whole  as  a  system 
has  been  gone  into. 

303... The  scarp  walls  of  outworks,  as  well  as  their  gor. 
where  they  are  exposed  to,  be  turned,  should  not  be  h\s*  than 
12  feet  high,  to  secure  them  from  a  sudden  open  assault. 

304:. ..Their  parapets  are  of  the  same  form  as  that  of  the  en- 
ceinte: and  fortlie  more  important  ones,  which  are  much  ex- 
pesed  to  the  artillery  of  the  assailant,  of  the  same  dimensions. 
Jn  t'  -  exposed,  the  thickness  of  the  parapet  may  be  re- 

duced to  L2  feet,  or  4  yards. 

~....T1m  terrepleins  of  the  smaller  outworks,  which  are  not 
habitually  armed  with  artillery,  should  not  he  less  than  8 
yards;  those  of  the  larger  should  not  he  less  than  1  * >  yard-. 

.".oi;...The  banquette-treads  of  outworks,  which,  like  the  ca- 
ponoieres  and  covered-ways,  require  a  palisading  for  their 
greater  security  from  utauU,  should  be  6  feet  wide. 

7...Ti  n  ati  u  .  PL  •:.  Figs.  1.  -1.  The  form  of  the  tenaille 
IS  that  of  CormoiitainirncV  front ;  the  magistral  of  it>  curtain 
being  parallel  to  that  of  the  curtain  of  the  enceinte,  ami  the 

the  prolongation  of  the  scarp  of  the 
tion  fao 

-...A  ditch    of    13    yard-  i.-  left    between    the    g  the 

tenaille  and  the  enceinte  curtain,  and  one  of  1 1  yard-  between 
each  of  its  wings  and  the  think.-.  Tile  magistral  of  ita  curtain 
is  horizontal,  and  1 .".  feet  above  the  crests  of  the  doable  capon- 
niere.  The  magistral  of  each  wing  is  a  broken  line,  the  lo 
point  of  it  being  13  feel  above  the  bottom  of  the  enceinte 
ditch.      1'  and  the  extremities  of  i: 

iteriof  crest  is  horizontal  throughout,  and  •  I  below 

the  ftl  of  tiie  enceinte  o.     The  thi< 

parapet,  \i  feet    The  w  idt  h 


11"  ex's  method. 

8.66  yards-  The  parapet  is  terminated  at  the  wings  by  tra- 
verses LS  feet  thick,  which  extend  from  the  interior  crest  .to 
the  .-carp  wall  of  the  wings;  the  top  of  each  traverse  is  on  the 
same  level  as  the  interior  crest  The  traverses  are  terminated 
toward  the  parapet  by  planes  of  l-l. 

809l..To  construct  the  principal  lines  of  the  tenaillefrom  the 
preceding  data,  first  draw  a  line  parallel  to  the  enceinte  cur- 
tain, and  18  yards  from  it.  for  the  gorge  of  the  tenaille  curtain  ; 
another  line  parallel  to  this,  and  at  s.'i»;  yards,  is  the  interior 
crest,  of  which  the  reference  is  (63.50),  as  it  is  4.60  feel  below 
the  enceinte  magistral  at  the  cui-tain. 

31<»... A  level  passage  at  31.50  feet  below  the  magistral  of 
the  enceinte  curtain  and  at  the  reference  (86.$0),  leads  from 

the  main  ditch,  between  the  enceinte  and  tenaille,  under  this 
last  work,  and  through  a  double  caponniere  in  the  main  ditch 
in  advance  of  it.  The  crests  of  the  caponniere  are  $  feet 
abdvethe  level  of  the-  passage  and  at  the  reference  (45.50)) 
and  the  magistral  of  the  tenaille  curtain  13  feet  above  these 
OTCStS,  and  at  the  reference  (5S.50).  The  interim-  Crest  of  the 
tenaille  having  the  reference  (63.50), "fs> therefore, ."»  feet  above 
its  magistral.  The  horizontal  distance,  then,  between  the 
magistral  and  interior  crest.  Art.  05,  is  12+3+1.5  =  10.5  ft., 
6r  6.50  yds.;  and  as  these  lines  are  horizontal,  their  projec- 
tions will  be  parallel  and  at  this  distance  apart. 

311. ..The  interior  crest  and  magistral  of  the  wing  will  result 
from  the  following  data:  The  scarp  wall  of  the  wing  extends 
to  the  to]>  of  the  traverse  reference  (63.50);  its  magistral  then 

descends  from  this  level  in  the  plane  of  1-1,  which  terminates 
this  traverse,  to  a  level  of  l;;  feet  above  the  bottom  of  tin-  en- 
ceinte ditch,  which;  being  at  this  part  8  feet  lower  than  the 
passage    of   the    double    caponniere,  and    at     reference  (33.50), 

will  give  (46.50)  tor  the  reference  of  the  lowest  point  of  the 
magistral  of  the  wing;  the  reference  of  .the  point  where  it  joins 
that  of  the  curtain  being,  as  already  determined,  (58.50); 

312...Tofind,  then,  the  lowest  point  of  this  magistral,  draw  a 
line  12  feet,  or  4  yard.-,  from  the  extremity  of  the  wing,  for  the 


NOIEET8    .Million.  Ill 

exterior  line  of  tlio  traverse;  parallel  t6  tins  lino  draw  another 
at  17  ft.  =  5.<i<;  yds.,  which  is  the  base  of  the  slope  of  l-l  that 
terminates  the  traverse,  where  tins  line  cuts  the  line  0/ defence 
is  the  required  points  The  horizontal  distance  between  thifi 
point  and  the  interior  crest,  calculated  in  the  usual  manner,  is 
li'-|-15-r-1.50=2s.:,o  k*9.G0  yds. 

318.».Describing,  from  the  point  just  found,  an  arc,  with  a 
radius  9.50  yards,  and  from  the  other  extremity  of  the  magis- 
tral another  arc,  with  a  radius  5.50  yards,  and  drawing  a  tan- 
gent to  these  ares,  it  will  he  the  inferior  erest  of  the  wings. 

314-.. .The  gorge  line  of  the  wing  is  not  drawn  parallel  to  the 
interior  crest,  but  determined  as  follows:  From  the  point,  of 
intersection  of  the  interior  crests  of  the  enrtain  and  Wings, 
descrihe  an  are  with  a  radius  8.66 yards;  from  the  point  when 
the  enceinte  enrtain  magistral  prolonged  cuts  the  interior  crest 
of  the  opposite  flank,  draw  a  line  tangent  to  this  are,  which 
will  he  the  direction  of  the  required  line. 

31 5.. .The  gorge  wall  rises  to  the  level  of  the  terreplein. 
That  which  terminates  the  wing  is  limited  by  the  planes  of  the 
parapet,  terreplein,  and  top  of  the  traverse,  and  is  termed  a 
proJUt  tr<tll,  from  the  form  of  its  outline. 

mi*!....\n Ai.Y-i-  of   Oeas  THE  Tenah.i  I  . 

The  teniiille  is  taott  important  as  a  mask  than  ns  a  defensive 
work.     I  the  postern  in  the  enrtain.  and  also  the  ma- 

ny of  the  flanks  and  curtain  from  the  enemy's  battel 
which  last  is  ;i!i  essential  point,  if  there  are  interior  retrench- 
ments resting  either  on  the  flank-  or  certain  of  the  enceinte, 
as  it  will  then  he  impracticable  for  an  enemy  to  turn  then 
he  cannot  make  a  breach  in  the  enceinte  behind  the  t.naille. 
.  e  work  it-  tire  bean  upon  the  ditches  and  their 
id  it  tie.  er  the  retn  at  of  the 

troops  from  the  ether  outwork.-.     When  the  ditch.  py  it 

indispensable  part  of  the  front,  as  t: 
fori:  run  he  :i--f  luhled  to 

mameu\  \  when  in  the  ditch*  -. 

3  1  7...  Yauhau    and    <  we   h.i\ 


112  Nnl/.ll'-     Million. 

the  relief  of  the  tenaille  as  not  to  mask  tin1  lire  of  the  flunks 
(»n  tlif  breach  in  the  bastion.  It  is  on  tins  principle  that 
Nouret  has  determined  the  position  of  its  interior  crest,  and 
placed  it  at  4.50  feel  below  the  magistral  of  the  curtain. 

31s. ..In  regulating  its  scarp  wall,  it  is  supposed  that  an 
enemy  would  attempt  an  assault  from  some  point  in  the  dead 
space  in  front  of  it  ^  and  its  height  is,  therefore,  arranged  so 
that  no  pari  of  it  shall  be  less  than  L3  feet  above  any  point 
that  the  enemy  might  then-  occupy, 

319...The  position  given  to  its  interior  crest  still  leaves  some 
portion  of  the  masonry  behind  it  exposed;  but,  were  the  ex- 
d  {'art  battered  away,  there  would  be  still  a  formidable 
height  of  scarp  left  to  the  enceinte,  the  parapet  of  which, 
also, 'would  be  l>nt  slightly  diminished  in  thickness  by  it.  The 
portion  of  the  enceinte  flank  exposed,  near  the  shoulder  angle, 
would  be  very  considerable  were  the  exterior  slope  of  the 
tenaille  parapet  extended  to  tin-  extremity  pf  the  wing;  it  is 

to  prevent  this  that  a  travels  is  here  placed. 

820.. .The  tenaille  is  seldom  armed  with  cannon,  although 
mortars  are  frequently  placed  in  it;  on  this  account  its  t>rr<- 
jiliin  is  feduced  to  s.,'>»>  yards. 

331.sJSvery  part  of  the  ditch  between  the  tenaille  and  cur- 
tain should  he  swept  hy  the  think.-.  It  is  to  satisfy  this  condi- 
tion that  the  gorge  line  of  the  wing  is  bq  drawn  as  to  be  seen 
hy  the  piece  that  flanks  the  curtain  of  the  enceihteJ 

322.. .The  tenaille,  although  procuring  decided  advantages  to 
the  bastioned  form,  deprives  it  of  one  of  its  characteristic 
points — that  of  flanking  every  part  of  the  ditch.  For,  in  frond 
of  the  tenaille,  there  is  a  dead  space,  where  an  assailant  could 

a-.-eiuhle    in    Safety  to    assault    it.      This    defect,  however,  is   of 

trifling  magnitude,  since,  were  the  tenaille  taken,  be  could  not 

e.-tahlish  himself  in  it  ;  and  the  width  given  to  the  ditch,  be- 
tween it  and  the  enceinte  Hank,  is  such  a>  to  preclude  any 
attempt  to    e-ealade  the  enceinte  from   the   top  of  the  tenaille. 

323.. .The  terreplein  of  the  tenaille  is  inclined,  for  the  pur- 
pose  of  defiling  it  from  the  enemy's  establishment  on  the  ter- 


NOIZI.I*-     M!    I  IK  Hi.  113 

replein  of  the  demilune  redoubt.    The  inclination  of  the  plane 
of  defilement  depends  on  the  arrangement  of  this  redoubt. 

824.. .Double  Caponwikbe.  PI.  3,  Figs.  1,  2.  The  paaaage 
of  the  double  caponniere  is  3.30  yards  wide  at  the  bottom, 
and  on  the  same  level  as  the  bottom  of  the  ditch  at  the  middle 
of  the  curtain  reference  (86.50).  The  interior  crests  of  this 
work  are  at  9  feet  above  the  bottom  of  the  passage ;  they  are 
horizontal,  and  their  reference  |  t5.50).  In  the  profile  of  the 
caponniere,  the  base  of  the  interior  slope  is  0.50  yards;  the 
banquette  is  2.0  yards  wide ;  and  the  base  of  the  banquette- 
slope,  3.0  yards;  the  horizontal  distance,  then,  between  the 
interim-  crest  and  the  foot  of  the  banquette-slope  is  5.50  yai 
which,  being  doubled  and  added  to  3.80  yards,  the  width  of 
the  passage,  gives  L4.30  yards  for  the  distance  between  the 
interior  crests,  The  crests  are  drawn  parallel  to  the  perpen- 
dicular of  the  front,  and  Limited  by  the  curtain  of  the  tenaille 
on  one  side  and  a  line  drawn  parallel  to  and  3.3<>  yards  within 
the  exterior  side  on  the  other. 

325. ..The  embankment  of  the  caponniere  is  terminated  on 
the  exterior  by  a  glads,  which  is  prolonged  to  the  bottom  of 
tin'  ditch.  This  glacis  is  determined  by  passing  a  plane 
through  the  interior  crest  of  the  capdhniere,  and  through  the 
shoulder  angle  of  the  interior  crest  of  the  opposite  bastion 
lowered  thn 

.••...']"■■.<  caponnien   is  terminated  toward  the  exterior  side 
by  a  profile  wall  along  the  lift ■.  at  8.30  yards  within  the 
terio  this  wall  is  prolonged  from  the  exterior  line  of  the 

banquette-tread  to  a  point  at   2.0  yards  beyond  the  interior 

*   this  point   the  direction  of  th<-  wall  is  changed, 
that,  being  prolonged,  it  may  cut  the  interior  oreel  of  the  i  n- 

v  flank,  at  a  point  LO  yard-  from  the  should'  r  The 

remaining  part  of  the  embankment  on  this  side  is  U  rmmated 
in  a  the  plane  of  which  is  through  the  inn 

•  of  the  enceinte  curtain,  and  through  a  line  on  the  bottom 
of  the  main  ditrh.  at   t.O  yards  within  the  exterioi 
plane  inl  -  in  a  Lineaft,  P  2,  which 


114  1*-    Ml  THOD. 

is  prolonged  to  it-  intersection,  &,  with  a  lino.  h<\  on  tlic  first 
glacis,  a1  6.66  yards  from  the  interior  crest.  A  part  oftne  first 
glacis  ie  terminated  at  this  lino,  by  a  plane  of  l-l  :  the  line  of 
intersection  of  this  plane  of  l-l  with  the  second  glacis,  ie  pro- 
longed to  intersect  ih<'  line  <•('  the  wall  directed  on  the  flank, 

which  gives  the  point  where  this  wall  terminal 

As  the  bottom  of  the  enceinte  ditch  has  no!  yet  been  fixed 

throughout,  its  intersection  with  the  first  glacifl  still  remains  to 
be  determined. 

."! •_'?.... \ \.\ i. v -i-  OFTHi  Double  Caponoteke.  The  caponmere 
serves  both  a^  a  commnnication  and  ;i>  a  defensive  work  for  the 
ditch.     As  the  former,  the  p  mould  admit  of  a  conve- 

nient circulation,  without  being  too  wide,  which  has  determined 
its  width  at  3.30  yards.  The  interior  crests  should  cover  the 
troops  within  the  caponniere  from  the  enemy's  establishments 
on  the  crest  of  the  bastion  covered-way  ;  a  relief  of  9  feet  lias 
been  found  sufficient  for  this  purpose. 

•'!i>S...As  a  defensive  work,  it>  tire  should  sweep  the  ditch. 
It  is  for  this  purpose  that  its  embankments  are  arranged  on  the 
interior  as  an  ordinary  parapet  ami  on  the  exterior  in  the  form 
of  a  glacis.  Its  banquette-tread  is  made  2.0  yards  wide,  as  it 
should  be  palisaded. 

329. ..In  order  that  the  embankment  of  the  eaponnniere may 

not,  by  its  relief,  form  dead  .-paces    in    the   ditch,  tin-   plane   <>t' 

the  first  glacis  is  arranged  so  as  to  he  sWepI  by  the  artillery 
fire  of  the  opposite  flank.  The  plane  of  the  second  glacis  and 
the  return  wall  are  so  arranged  as  to  he  swept  by  the  lire  of 
the  Curtain  and  of  a  part  of  the  flank. 

The  portion  of  the  first   glacis,  near   the    extremity,  is  made 

into  ^glacis  o&wpe,  Leaving  a  sufficient^  thickness  of  parapet  to 

cover  the  passage. 

'■VM  I. .  AI  aoisti:  w.s    oi      I  >im  1 1  i  n  i;    Scaup    AM>    CotTNTEBSOAJRP. 

PI.  3,  Fig.  3.    To  construct  the  magistral  of  the  demilune,  two 

points  are  taken  on  the  exterior  side  at  103  yards  from  the  per- 
pendicular; through  these  points  perpendiculars  are  drawn  to 
the  exterior  side ;  the  points  where  they  cut  the  magistral  of 


NOIZKlV    Mil  hod.  115 

the  bastioD  faces  arc  joined,  and  on  this  line  an  equilateral 
triangle  is  constructed,  its  sides  will  give  the  directions  of  the 
magistral  of  the  demilune.  The  extremity.  1>.  of  the  demilune 
face,  is  found  by  drawing  a  line  at  11  yards  without  the  exte- 
rior side. 

The  counterscarp  of  the  demilune  is  parallel  to  the  scarp,  and 
at  L8  yards. 

331...C<TN  U  Km  AIM"    Of    THE     K\<  Tr\TK.       PI.    3,    Pig.  3.      To 

struct  the  counterscarp  of  the  enceinte,  an  arc  is  described 

from  the  salient  of  \\\q  bastion,  with  a  radius  of  26  yards;  a 
perpendicular,  ///'.of  6.60  yards,  is  drawn  to  the  demilune 
face;  if  a  tangent  be  now  drawn  to  the  are,  and  a  perpendicu- 
lar be  demitted  from  the  point/",  on  the  tangent,  their  point 
of  intersection./1',  should  fall  on  the  line  drawn  through  the 
extremity  of  the  double  caponniere,  parallel  to  the  exterior 
side.  The  point. y.  is  found  l>y  constructing  the  curve,  which 
i>  the  locus  of  the  above  conditions.  The  arc,  with  the  tan- 
gent drawn  through/*,  is  the  magistral  of  the  counterscarp. 
332. ..III. DOUBT   "K   nil.    Pi-.-i  xti.uiNo   PlAOE  OF  Ai:M-.      PI.    3, 

8.  To  determine  the  magistral  of  the  redoubt  of  thereon." 
tering  place  of  arms,  a  line  i>  drawn  through  the  point,  ft,  of 
the  demiluni  iremity  of  the  curtain,  and   pro> 

longed  beyond  the  demilune  counterscarp.     A  point.  </.  i.-  next 
taken  on  the  perpendicular,  at  5.0  yards  from  the  demilune 
salient  ;  and  through  this  point  and  a  point,  <'.  assumed  on  the 
demiluni  counterscarp,  an  indefinite  line  is  drawn.    A  Ww- . 
<1.  is  next  drawn,  making  an   angle  of  60"  with  the  line  a  <\ 

Two    lines,    '''/'and  •''",  :uv    drawn,  the    first    parallel  t<>  <•  </. 

and  4.30  yards  from  it :  I  >nd  parallel  I 

lg  from   it.     It'  the  point  of  into  i 
lines  falls  on  the  line  drawn  through  ft,  it  will  he  the  angular 
point  <•)  the  redoubt  :  and  the  line  •'  <1\  the  magistral  <•!' 

If  the  point  ' '.  d",  ]  on  the  line  drawn 

through  1>,  then  ..  I   point,  <',  most   be  chosen,  and  the 

sane  ii  mad-'.     The  differ 

of  a  curve,  which    il   I 


1  10  NOl/.l.l'-     Million. 

conditions;  and  the  intersection  of  tins  curve  with  the  line 
drawn  through  5,  will  give  the  required  point.  Having  the 
face  (■'</'.  tin-  other  face  is  determined  as  follows:  a  line  is 
drawn  parallel  t<»  tin-  demilune  counterscarp,  and  at  27.0  yards 
from  it  ;  a  point  is  found  on  this  line,  at  T.s;;  yards  from  <■'  </'; 
from  this  point,  with  a  radius  of  7.83  yards,  an  m-c  is  described^ 
a  tangenl  drawn  to  this  arc,  from  a  point  on  the  interior  crest 
of  the  bastion  face,  at  L3  yards  from  the  pancoupe,  is  the  di- 
rection of  the  required  lace.  </'(/",  which  is  terminated  at  the 
bastion  counterscarp. 

::■•::;. ..i'l.  3,  Fig.  ::.  and  PI.  I,  Fig.  1.  The  ditch  of  the  re- 
doubt is  horizontal;  and  the  reference  of  its  bottom  is  deter- 
mined by  supposing  the  plane  of  the  superior  slope  of  the 

bastion    face   to    be    prolonged    to    the   enceinte    counterscarp, 

finding  the  reference  of  the  point,  d",  in  this  plane,  and  taking 
a  point  4.50  feet  below  this;  the  reference  thus  found  is 
pT.fiu).  The  scarp  wall  of  the  redoubt  is  13  feet  high,  the 
reference  of  its  magistral  will,  therefore,  be  (70.90). 

334. ..The  salient  of  the  interior  crest  is  5.33  feet  above  the 
magistral — its  reference  is,  therefore,  (76.23) ;  and  its  projec- 
tion is  evidently  the  point  which  we  have  already  determined, 
at  7. S3  yards  from  the  magistral;  The  interior  crest  of  the 
fact-,  d'  </",  has  a  slope  of  two  feet  from  the  .salient  to  the  ex- 
tremity of  this  face,  which  condition  fixes  the  extreme  point  of 
the  interior  crest  at  7.10'  yards  from  the  magistral. 

Having  the  interior  crest  of  one  face,  that  of  the  other,  <t  d\ 

is  found  from  the  Scale  of  declivity  of  the  plane  of  the  interior 
crest.  This  scale  is  drawn  parallel  to  the  bastion  capital,  and 
since  we  have  already  found  two  points  of  the  interior  crest, 
by  referring  them  to  this  scale  we  can,  as  in  the  case  of  the 
bastion,  Art.  294,  determine  any  required  point  of  the  other 
face. 

885.. .A  small  Hank  of  6.0  yards  is  made  perpendicular  to  the 
line  c  c",  the  line  of  the  profile  wall  of  the  face,  <•'  </'. 

336.. .The  tenvplein  of  the  redoubt  is  8.66  yards  wide;  its 
gorge  is  revetted  with  a  wall  13  feet  high. 


noizet's  METHOD.  1 1  7 

337.. .Analysts  of  the  Redoubt,  eto.  Having  given  the 
construction  of  the  principal  linos  of  the  redoubt,  we  will  now 
give  the  reasons  in  snpport  of  them. 

388... We  tir.-t  observe  that,  on  account  of  the  ditch  between 
tin-  tenaille  and  the  enceinte  flank,  a  breach  might  be  opened 
in  the  curtain,  by  means  <>i  a  battery  established  on  the  glacis 
of  the  reentering  place  of  arms,  if  there  was  no  mask  between 
tlic  ditch  referred  to  and  this  glacis.  By  placing  the  angle,  c, 
of  the  redonbt  on  the  line  drawn  through  the  extremity  of  the 
curtain,  and  the  extremity,  6,  of  the  demilune,  it  is  readilyseen 
that  these  two  works,  bo  combined,  cover  the  opening  left  by 
the  ditch;  since  it  -will  he  necessary  to  battle  down  either  the 
angle  </,  or  the  angled,  to  unmask  the  curtain.  The  means 
here  resorted  to  is  of  frequent  use  in  fortification ;  and  the 
problem  may  be  thus  stated:  a  lint  beinggiven,  which  ispar^ 
1'inUy  covered  by  an  estietiftg  mast  from  foes  in  <<  given  direc 
//'<>}>,  in  mterposi  another  mate  which,  combined  with  tfu  first, 
shall  entirely  mask  tht  given  line. 

We  have  thus  established  that  the  point.  <■',  slrall  be  found 
on  the  line  drawn  through  b  and  the  extremity  of  the  enceinte 
curtain. 

The  communication  along  the  gorge  of  the  redoubt  to  its 
ditch,  is  by  mean-  of  stairs  placed  along  the  profile  wall,  <■'  <". 
The  width  of  the  stair,-  it  2.0  yards.  The  stairs,  like  all  other 
communications,  to  be  safe,  must  be  covered  from  the  enemy's 
lire.     The  point  where  the  enemy  can  establish   himself,  to 

fire  mi   the  -tail'.-,   tfl  along  the    CTCSt    of    the    demilune    Cover*  d- 

way,  around  the  salient  place  of  arm-.  It  i^  readily  seen, 
from  the  position  of  the  stairs  and  the  demilune,  thai  this 
work  will  partially  cover  the  stairs;  and,  therefore,  we  rdiall 
only  have  to  Interpose  some  other  mask,  combined  with  it.  to 
attain  t:  i  ;.-k  n-.'J  ii  the  point  '•,  w 

Lj  the  angle  of  masonry  formed  by  the  counterscarp  walli 
demilune  and  redoubt;  the  ditch  of  the  redoubt  being 

The  position  of  the   point  </.  through  which 
on    the    exterior  the 


118  N.'izi  r">   METHOD. 

/ 

demilune  parapet,  that  the  Use  of  are  drawn  through  it  will 
paai  "Vrr  a  man's  head  at  the  t <  •  j »  of  the  Btairsi 

839.. .The  angle,  <\  between  the  profile  wall  and  face  wall, 
la  made  60°,  as  this  is  the  minimum  angle  for  masonry,  to  ■- 
it  sufficient  strength.    The  minimum  is  here  taken  to  bring 
the  face,  <•' o?,  as  far  in  aa  possible,  and  thereby  make  the  reen- 
tering as  deep  as  the  case  will  admit  of. 

340...The  object  of  the  redoubt  is  to  strengthen  the  covered- 
way,  and  iweep  with  its  fire  the  enemy's  establishments  on  the 
glacis  of  the  demilune.  The  principal  works  on  this  glacis 
arc  the  breach  and  counter-patteries,  which  occupy  a  Bpace  of 
about  17.0  yard.-,  estimated  from  the  crest  of  the  glacis  j  if  to 

this  we  add   L0  yards,  for  the   mean  width  of  the  co\eivd-way, 

we  obtain  the  distance  27.0  yards,  which  is  the  least  distance 
that  the  salient  of  the  redoubt  can  be  from  the  counterscarp 

of  the  demilune,  to  sweep  the  entire  flank  of  the  batteries. 
341. ..The  direction    given    to  the    face,    <l'   <1'\  is   such    as   to 

allow  of  its  being  flanked  by  the  bastion  face.  The  face  is 
thrown  out  as  far  toward  the  salient  of  the  bastion  covered- 
•way  as  possible,  for  the  purpose  of  crowding  the  space  along 
the  crest  of  this  covered-way,  which  the  enemy  requires  for 
his  batteries. 

342. ..The  redoubt  being  directly  in  front  of  the  bastion  face, 
its  relief  "should  be  bo  redueed  thai  the  fire  of  this  face  may 
not  be  too  much  masked.  To  effect  this,  we  commence  by  es- 
tablishing the  bottom  of  its  ditch,  so  that  the  point  of  it 
nearest  the  bastion  may  just  be  Been  by  the  musketry  lire  of 
the  face;  we  then  adopt  nearly  a  minimum  relief  of  scarp 
wall;  finally,  we  arrange  the  interior  crest  of  one  face,  so  as 

to  allow  no  exterior  slope  at  one  extremity,  and  make  the 
other  at  the  salient  2  feet  higher.  This  slope  of  -  feet  and  the 
direction  given  to  the  scab'  of  declivity  of  the  interior  crest, 
determine  a  plane  of  defilement  for  the  redoubt,  the  prolonga- 
tion of  which  will   pas>  at  about   3  feet    above    the   salients  of 

the  two  demilunes,  which  are  symmetrically  situated  with 
respect  to  the  bastion  capital.     This  is  done  in  accordance  with 


NOIBET's    Million.  119 

a  principle  generally  adopted,  that  when  one  work  is  less  ad- 
vanced than  another,  and  commanded  by  it,  ijhe  plane  of  its 
interior  crest  prolonged  should  pass  3  feet  above  the  points 
which  the  enemy  can  occupy  on  the  advanced  work — which, 
from  the  nature  of  fche  attack,  must  fall  first  into  his  possession — 
so  that  he  may  not  have  a  plunging  fire  into  the  retired 
work,  from  his  establishments,  which  arc  generally  about  3 
feet  above  the  parapet  of  the  work  occupied. 

343. ..The  small  flank  of  6.0  yards  perpendicular  to  the  pro- 
file wall,  is  to  obtain  a  reverse  fire  on  the  breach  made  in  the 
demilune.    The  gorge  of  the  redoubt  is  revetted  to  secure  it 

from  an  assault. 

344.. .Di  mii  i  m    Redoubt;    PI.  3.  Fig.  B,  and  PI.  4,  Figs.  I. 

2.  The  salient  of  the  redoubt  is  33.0  yards  from  the  magistral 
of  the  demilune  ;  finding  a  point  on  the  perpendicular,  at  this 
distance  from  the  magistral,  we  obtain  the  salient.  The  magis- 
tral <>f  the  tace  is  found  by  drawing  a  line  from  this  point  to 
the  interior  shoulder  angle  of  the  bastion. 

.".!.*>... To  find  the  portion  of  the  interior  crests  of  the  face, 
the  reference  of  the  magistral  must  be  given,  and  the  scale  of 
declivity  of  the  plane  of  the  interior  crest.  To  determine  the 
first,  the  salient  of  the  demilune  interior  crest  is  placed  at  3 
feet  below  tbat  of  the  enceinte  curtain:    this   giv  for 

the   reference   of  this    point      The    salient  of  the    magistral    of 

the  redoubt  is  fixed  at  B  feet  below  the  salient  of  the  demilune, 
which  gives  it-  reference  (70.0).  Xhe  magistral  Blopes  from 
the  salient  toward  the  exterior  side,  and  this  Blope  i>  arranged 
s<>  that  the  point  where  the  magistral  cuts  the  exterior  side 
shall  be  5.70  feet,  or  1.90  yards  lower  than  the  salient;  the 
rence,  then,  of  this  point  will  be  (64.80).  Having  thus 
point-  of  thi  Tab  ita  position  is  fixed. 

846...TV)   determim    now  the  interior  crest,  a  paneoupe*  of 
4.:'."  yards  :-  made  in  the  salient  of  the  redoubt,  and  thi-  com- 
mands the  salient  of  tie'  demilune  by  1 .6  R  et.    T 
then,  of  the  paneoup  Prom  the  pan*  to  the 

the  redoubt,  which  is  on  tie 


120  Nnl/.l   I   |    MKTHOD. 

ofNthe  interior  crest  lias  a  -lope  of  1.5  feet,  and  its  scale  of  de- 
clivity i>  parallel  to  tin-  perpendicular.  To  find  the  crest  from 
tin-  above  'lata,  it  may  be  ebeerved  that  the  problem  is  similar 

to  the  one  already  wived,  Art.  •_".'!.  in  the  case  of  the  bastion; 
except  here,  tin-  magistral  being  an  inclined  line,  the-  distance 
of  any  one  ofita  points,  to  the  point  on  the  interior  crest,  con- 
tains! in  a  profile,  is  not  known,  sin^e  only  Ope  of  the  points  is 
n.  The  following  is  the  method,  which  applies  to  all  simi- 
lar eases  for  doing  this:  It  will  he  observed  that,  if  the  foot  of 
the  exterior  slope  he  drawn,  it  will  have  the  same  slope  as  the 
magistral.  Through  the  foot  of  the  exterior  slope,  then,  which 
is  known,  th* plane  of  the  exterior  slope  whose  inclination  is 
1-1,  is  passed.  If  any  horizontal  line  be  now  drawn  in  this 
plane,  the  horizontal  distance,  Art.  294,  between  this  line  and 
a  known  point  of  the  interior  crest,  contained  in  a  protile,  can 
be  readily  found. 

To  apply  this  to  the  ease  in  point,  first  drawn  the  foot  of  the 
exterior  slope,  which  is  0.50  yard  from  the  magistral;  the  re- 
ference of  this  line  at  the  salient  is  (70.0),  and  at  the  gorge 
(G4.30).  To  obtain  the  horizontal  of  the  plane  of  the  exterior 
slope  whose  reference  is  (70.0),  describe  from  the  point  (04.30) 
an  arc,  with  a  radius  5.70  feet,  or  1.90  yards;  the  tangent 
drawn  to  this  arc  from  the  point  (70.0),  is  the  required  line. 
The  reference  of  the  pancoupe  being  (79.50^,  its  distance  from 
this  horizontal  line — the  thickness  ot  the  parapet  being  20.0 
feet — is  26,1?  fret,  or  S.72  yards;  and  the  reference  of  the  in- 
terior crest  at  the  gorge  being  (78.0),  its  distance  from  the 
same  line  is  8.22  yards;  the  two  points  thus  found  lix  the  posi- 
tion of  the  interior  crest  of  the  face. 

347.. .The  redoubt  is  made  with  flanks,  the  interior  crests  of 
which  are  parallel  to  the  perpendicular,  22.0  yards  in  length. 
To  find  the  flanks,  draw  a  line  parallel  to  the  exterior  side,  and 
at  22.0  yards;  where  this  cuts  the  interior  crests  of  the  faces 
will  hi'  the  interior  shoulder  angles  of  the  redoubt,  from  whieh 
the  flanks  are  drawn  parallel  to  the  perpendicular. 


t 

*  NOIZEX'S    METIImIi.  121 

The  magistral  of  the  flank  is  horizontal,  its  position  is,  there- 
fore, easily  found. 

348. ..Joining  the  point,  b.  of  the  demilune,  with  the  extrem- 
ity of  the  interior  erest  of  the  flank;  the  direction  of  the  wall 
which  terminates  the  flank,  the  ditch  of  the  redouht  and  the 
extremity  of  the  demilune  is  found. 

349. ..The  terreplein  of  the  redouht  along  the  face  is  8.66 
yards  wide;  along  the  flank  the  width  is  11.0  yards.  This 
terreplein,  which  is  8  feet  below  the  plane  of  the  interior 
crest,  is  called  the  >'/>/»/',  to  distinguish  it  from  the  remaining 
interior  space,  called  the  lower  A  rr> j  A///,  and  which  is  13  feet 
below  the  apper.  A  portion  of  the  upper  terreplein,  for  a 
Length  of  about  14.0  yards  from  the  extremity  of  the  flank,  is 
sustained  by  a  wall  of  masonry.  A  portion  of  the.  interior 
space  between  the  terrepleina  of  the  two  flanks,  for  about  6.0 
yards  from  the  exterior  side,  is  excavated  to  the  bottom  of  the 
ditch. 

350. ..The  upper  terreplein,  along  the  face,  is  connected  with 
the  lower  by  a  slope  of  f.  Two  ramps  3.30  yafdfl  wide,  with 
a  slope  of  1-0,  connect  the  two  terrepleins.  The  details  of 
these  constructions  are  best  studied  from  PI.  4,  Fig.  1.  The 
scarp  wall  of  the  redoubt  is  l<i.."><>  feet  high. 

351... Analysis,  in.,  <>|.  the  Dimium.  Rbdodstt.  As  the 
object  of  the  demilune  redoubt  lias  been  already  explained, 
the  reasons  for  the  constructions  employed  in  determining  it> 
dimensions,  etc.,  only  remain  to  be  stated. 

352.. .The  redoubt  shonld  be  as  advanced  as  possible,  t<> 
in  reverse  the   lodgments  of  the  enemy   on   the  glacis  of  the 
collateral  works.      To   effect    this,  it>    salient    is   taken    ;tt 

yards  from  the  demilune  magistral  ;  this  distance  is  sufficient 

to  allow  their  proper  dimension,-  to  the  parts  Of  the   demilune. 

..The  Uic,'  of  the  redoubt   is  directed  on  the  interior 

shoulder  angle  of  the  bsstion,  to  have  its  ditch  flanked  by   the 

354.. .In  placing  the  Balient  of  the  magistral  at  s  feet  below 

the  salient  of  the  demilune,  the  top  of  the  scarp  wail  will  be 
16 


1  •_'•_'  N.H/.Kl  B    METHOD.  * 

nearly  on  the  level  with  the  demilune  terreplein.  This  arrange- 
nR'iit  will  force  in i  enemy,  lodged  on  the  demilune  terre- 
plein, either  to  Lower  hie  battery,  to  effect  a  breach  in  the  re- 
doubt, or  else  \<<  employ  a  mine  for  this  purpose;  either,  ofl 
which  operations  will  coat  him  much  labor  ami  Loaa  of  time* 

355...The  LeaM  command  ha?  been  given  to  the  redoubt  over 
the  demilune,  to  enable  the  fire  <>i'  the  redoubt  to  sweep  the 
demilune  terreplein-  This  command  of  L.50  feet,  with  the 
slope  given  to  the  plane  of  the  interior  crest,  will  prevent  an 
enemy  from  having  a  plunging  lire  into  the  redoubt  from  his 
Lodgments  in  the  demilune. 

35G...Thc  flanks  of  the  redoubt  are  principally  to  procure  a 
reverse  lire  on  the  breach  in  the  bastion  face;  their  length  es- 
timated for  8  guns, 

The  piece  nearest  the  extremity  of  one  flank  should  be  cov- 
ered by  the  extremity  of  the  opposite  flank,  from  the  reveres 
fire  which  might  come  through  the  redoubt  from  the  enemy's 
lodgment  on  the  bastion   covered-way. 

The  terreplein  of  the  fiank  is  made  11.0  yaVls,  as  it  is  ha- 
bitually armed. 

:;.".7...In  the  outworks,  wherever  it  can  conveniently  be  done, 
bomb-proof  arches  should  be  made,  to  serve  as  magazines, 
shelters,  etc.  This  point  has  been  effected  in  the  redoubt,  by 
the  position  given  to  the  lower  terreplein;  by  this  mean.-,  sul- 
lieient  space  is  gained  under  the  flank  for  a  bomb-proof  shelter; 
The  terreplein  of  the  flank  is  sustained  by  a  wall,  which  is  the 
interior  facing  of  the  shelter. 

:!5S...Tli6  scarp  wall  of  the  redoubt  might  have  been  re- 
duced to  the  minimum  dimension  of  12  feet.  But,  on  account 
of  its  importance,  and,  also,  not  to  diminish  too  much  the  in- 
terior space,  it  has  been  found  that  the  dimensions  adopted, 

lt;..")0  feet,  best  satisfy  the  requisite  conditions.  The  top  of  the 
wall  sloj.es  toward  the  gorge,  so  that  at  the  shoulder  angle  it 
may  be  about  4  feet  lower  than  at  the  salient;  the  object  of 
this  is,  to  expose  as  small  a  portion  of  the  wall  as  possible  to 
the   eneinv's  tire   through   the   demilune   cut,  which,  from  its 


t 
Nm/.i  t\  Minion.  1_':; 

width,  might  admit  of  a  breach  being  made  in  the  redoubt, 
through  it.  from  flbe  enemy's  lodgment  on  the  reentering  place 
of  arms.  It  will  be  seen  further  on,  how  the  scarp  of  the  re- 
doubt is  covered  by  the  bottom  of  the  cut. 

.'^•...DrMii.rxK  „am>  us  Cut.  PI.  3,  Fig.  8,  and  PI.  4,  Pig. 
1.  To  return  now  to  the  demilune,  and  finish  what  relates  to 
it  and  the  cut  in  Its  ficfe;  % 

86O...T0  construct  tin-  scarp  of  the  cut,  the  face,  c'  d\  of  the 
redoubt  of  the  reentering  place  of  arms,  is  produced  to  infer- 
tile magistral  of  the  demilune;  joining  this  point  with  the 
interior  shoulder  angle  of  the  demilune  redoubt,  the  magistral 
of  the  scarp  is  obtained. 

B61...The  exterior  width  of  the  cut  is  found  by  setting  off 
6.00  yards  on  the  demilune  magistral,  from  the  point  where  it 
is  intersected  by  the  face,  <■'<!'.  To  obtain  the  interior  width, 
an  are.  with  the  radius  of  L0  yard.-,  is  described  from  the  ex- 
terior shoulder  angle  of  the  demilune  redoubt;  a  tangent  i.- 
drawn  to  this  are.  parallel  to  the  face  of  the  redoubt:  this  tan- 
gent gives  the  direction  of  a  wall  which  limits  the  cut  on  the 
interior,  and  also  the  portion  of  the  demilune,  from  the  cut  to 
the  extremity  of  the  face.  From  the  point  where  the  magis* 
tral  of  the  cut  intersects  the  tangent,  set  off  11.0 yards,  which 

is  the  width  of  the  cut  on  the  interior.  This  point  joined  with 
the  point  on  the  exterior,  gives  the  counterscarp  of  the  cut. 

S68...A  parapet  BOfeet  thick  is  made  behind  the  scarp  of  the 

cut.      'I'll.'  relief  of  this   parapet    IS    so    determined  that,  at  the 

highest  point  of  the  magistral,  which  is  the  point  on  the 

.  there  shall    he  no  exterior  slope  :  which  places  the  interior 

cr.  -t  ::.::::  feet  above  the  magistral  at  this  point.    The  Bcarp 

wall  itself,  at  this  point,  is  1  •">  let  ahove  the  bottom  of  the  cut 
on  the  interior:  and   the  interior  line  of  the  bottom    i-  !■'■ 
nearly  above  the  bottom  of  the  ditch  of  the  redoubt.     'I 
conditions  ti\    the   reference  of  this   point  of  the  magistral  at 
(76.17).     The  interior  crest,  which  is  horizontal,  is  therefore, 
at  ti  ' 

.The  bottom  of  the  cut  has  1  from 


124  trODSBrfl    Ml  ll!"l>. 

tlic  interior  to  fhe  demilune  scarp;  and  the  magistral  of  the 
cut  is  parallel  to  the  bottom  and  at  13  feel  above  it.  This 
gives  the  reference  of  the  exterior  point  of  the  magistral 
(71.37):  The  magistral  of  the  demilune,  from  this  exterior 
point  to  the  point  5,  is  heM  horizontal  and* at  the  same  refer- 
ence (71.37),  'l'li*'  parapet  of  this  portion  of  the  demilune 
face  is  Ldfeet  thick;  its  interior  crest  ie  determined  by  passing 
a  plane  through  the  interior  ereet  of  the  parapet  behind  the 
cut,  ami  allowing  the  prolongation  of  this  plane  to  pass  8  feel 
above  the  demilune  salient.  The  preceding  data  aiv  sufficient 
to  determine  the  lines  in  question. 

36 1...A.N  \i.y>i-  oi  i  in:  Out.  The  cut  isolates  the  pari  of  the 
demilune,  near  the  extremity  of  the  face,  from  the  salient 
portion  ;  this  part  being  arranged  with  a  parapet  behind  the 
cut,  can  be  defended  after  the  enemy  has  effected  a  Lodgment 
on  the  demilune  salient.  The  cut  thus  prevents  the  enemy 
from  driving  the  besieged  from  the  redoubt  of  the  reentering 
place  of  arms;  which  he  might  do,  were  the  whole  demilune 
to  fall  at  once  into  his  possession. 

365. ..The  position  of  the  cut  is  so  determined  as  to  allow  the 
face  of  the  demilune  redoubt  to  flank  the  face,  d  </'.  Widen* 
ing  the  cut  on  the  interior  facilitates  this  object. 

By  making  the  interior  line  of  the  bottom  of  the  cut  13  feet 
above  the  bottom  of  the  ditch,  the  scarp  of  the  demilune  re- 
doubt is  partly  covered;  and,  at  the  same  time,  an  obstacle  is 
placed  in  the  way  of  an  enemy,  who  might  attempt  to  carry 
the  work  behind  the  cut  by  first  getting  into  the  cut. 

366. ..It  will  be  seen,  in  examining  the  demilune  ditch,  that 
the  slope,  4.80  feet,  given  to  the  bottom  of  the  cut,  still  leaved 
a  height  of  15  to  18  feet  between  the  exterior  line  and  the  bot- 
tom of  the  demilune  ditch,  which  will  secure  the  cut  from  an 
assault  on  that  side.  The  object  of  this  slope  is  chiefly  so  to 
diminish  the  height  of  that  part  of  the  demilune  scarp,  from 
the  cut  to  the  point  b,  that  it  may  not  be  exposed  to  a  baft. -ry. 
which  can  be  placed  on  the  glacis  of  the  reentering  place  of 
arms. 


NoI/.Kl'.-     Ml  THUD.  1  •_'."» 

367... As  to  the  interior  crest,  it  is  placed  as  low  as  possible, 
and  is  arranged  to  cover  the  interior  from  the  plunging  tire  of 
the  eneiiiv'w hen  established  on  the  demilune  salient. 

368...Di:miia'nk.  PI.  4,  Pig.  2.  To  return  to  the  demilune, 
of  which  only  the  magistral  and  the  relief  of  the  interior 
crest  at  the  salient  have  been  determined. 

The  magistral  at  the  salient  is  placed  11.40  feet  below  the 
interior  crest ;  and  as  the  reference  of  the  latter  is  (T8.0)j  the 
reference  of  the  former  will  be  (66.60).  The  magistral  has  ■ 
slope  of  1.50  feet  from  the  Balient  to  the  cut;  and  the  interior 
ores!  is  parallel  to  the  magistral  ;  this  condition  will  determine 
the  interior  crest  when  the  salient  is  known  ;  and  this  is  ar- 
ranged so  as  to  have  a  pancoupe*  of  4.80  yards. 

The  scarp  wall  of  the  demilune  is  22.50  feet  high. 

869*..The  terreplein  is  11.0  yards  wide.  A  ramp.  3.30  yards 
wide,  having  a  slope  of  1-6,  leads  from  the  ditch  of  the  demi- 
lune redoubt  to  the  demilune  terreplein.  The  position  and 
arrangement  of  the  ramp  are  shown  in  PI.  4,  Fig.  2. 

870.. .The  terreplein  is  finished  by  a  slope  of  earth,  instead 
of  being  sustained  by  a  wall.  This  slope  is  thus  arranged : 
the  part  terminating  the  ramp  is  a  plane  of  1-1  :  the  position 
in  the  angle  is  formed  by  an  inclined  cylindrical  surface,  which 
touches  the  two  interior  lines  of  the  terreplein  :  the  width  of 

the  ditch  at  the  salient  of  the  redoubt,  terminated  by  the  1. .•!-.• 

of  the  cylinder,  is  4.-';^  yards.  The  remaining  portion  of  the 
slope  is  formed  of  a  warped  surface,  the  (dement.-  of  which 
are  horizontal,  connecting  the  cylinder  and  the  plane  of  1-1. 
Thi.-  construction  i.-  purely  arbitrary  ;  the  object  being  to 
have  the  portion  of  the  slope  in  the  salient  as  gentle  a-  practi- 
cable, so  that  this  pint  may  *  i  ramp  tor  infantry. 

-7 1.. .An  a  i  \  -:-  "i  mi    I  )i  miii  m  .  i  k  .     The  principal  prop- 
erties of  the  demilune  were  mentioned  in  describing  <  !ormon- 
method;  and  it  was  there  observed  that  he  improved 
upon  Vauban'a,  by  augmenting  the  dim-  f  'lie  demi- 

lune.    Engineers,  sine*  <  ortnontaingne,  finding  that  the  d. 
lunej  .-till  admitted  of  being  enlarged   with  .  ave 


llT,  .NMl/l.lV     Mi    II  K.|i. 

accordingly  bo  determined  its  dimensions,  thai  it  may  be  tin-own 
bo  far  to  the  front  as  will  still  place  the  breach,  which  an  en- 
emy may  make  in  it-  face,  within  the  range  of  the  musketry 
of  tin-  bastion  face.  In  large  fronts,  like  this  nnder  considera- 
tion, the  demilune  may  !>(■  thus  made  to  cover  about  80  yards 
of  the  bastion  faces  from  the  Bhoulder  angle,  and  thuB  secure 
retrenchments  resting  against  this  part  from  being  turned  by  a 
breach  made  near  the  Bhoulder  angle. 

872...These  considerations  limit  the  salient  angle  of  the  demi* 
lune  to  60°,  and  place  the  Balient  at  not  more  than  210  yards 
from  the  bastion  face,  as  this  distance  will  bring  the  breach  at 
about  180  yards  from  this  face,  or  within  the  effective  range  of 
musketry. 

373"...The  demilune  thus  arranged  places  the  bastions,  In  all 
cases,  in  strong  recnterings;  but  when  the  angles  of  the  poly- 
gon are  very  obtuse,  the  faces  of  the  bastions*  prolonged,  also 
fall  within  the  salients  of  the  demilQnes,  and  arc,  therefore, 
not  easilv  enfiladed.  The  fire  from  the  demilune  Is  very  effec- 
tive on  the  enemy's  works  along  the  bastion  capitals.  Finally, 
it  is  a  work  of  which  the  enemy  can  only  obtain  possession 
after  great  labor  ami  loss  of  time;  and  when  carried,  it  is  with 
great  difficulty  that  he  can  render  it.  tenable,  as  it  is  exposed 
to  the  fire  of  the  enceinte,  within  a  short  range. 

374.. .The  demilune,  with  these  advantages,  is  not  without 
defects.  Its  faces,  from  their  position,  are  exposed  to  an  enti- 
ladingfire;  it  deprives  the  curtain  of  all  action  on  the  exte- 
rior ground  ;  and  it  is  only  when  the  angles  of  the  bastion  arc 
very  open,  that  the  rednterings  formed  by  the  demilunes  be- 
come of  a  formidable  character.  The  glacis  6f  the  demilune 
covered-way  forms  a  ridge,  which  is  serviceable  to  the  enemy 
by  masking  ''is  works  on  one  side  of  the  ridge  from  the  fire  of 
the  collateral  works  on  the   other. 

Having  noticed  these  general  properties  of  the  demilune, 
the  further  particular  constructions  may  be  examined. 

375...In  terminating  the  lace  at  1  1  .< >  yard.-  from  the  exterior" 
side,  a  passage  made  along  the  extremity   of  this  face,  and  a 


not/kt'k  METHOD.  127 

face  cover  for  the  bastion,  of  which  mention  will  be  made  far- 
ther mi,  are  allowed  for;  moreover,  the  flack  of  the  demilune 
redoubt,  intended  to  defend  the  breach  in  the  bastion  face  by 
a  reverse  tire,  is  unmasked  by  it. 

•">7<!...The  command  <>f  the  curtain  over  the  demilune  is  re- 
duced to  the  minimum  ;  and  to  obtain  as  much  interior  c|iacc 
lor  the  demilune  reddidit  as  practicable,  the  height  of  the  in- 
terior crest  above  the  magistral  is  fixed  at  11.4<>  fees,  the  interior 
space  evidently  depending  on  this  height.  The  terreplein  is 
reduced  to  11.0  yards,  partly  for  the  same  reason,  and  partly 
to  give  an  enemy  great  trouble  in  establishing  a  battery  on  it; 
BSj  to  do  this,  he  will  be  obliged  to  cut  away  a  part  of  the  par* 
Spot,  and  will  thus  expose  the  rear  of  the  battery  to  the  fire 
from  collateral  works. 

.'!77...The  terreplein  is  terminated  by  a  slope  of  earth,  for 
omy,  and.  al.-o.  because  this  slope  is  favorable  to  offensive 

movements  made  to  drive  the  enemy  from  the  breach. 

:;7v...It  is  not  probable  that  an  enemy  would  attempt  to 
carry  the  demilune  by  escalade  ;  it  i>  well,  however,  to  pro- 
vide against  inch  an  attempt  in  bo  important  a  work;  it  is 
chiefly  on  this  account  that  the  scarp  wall  is  made  '-'•_,.7'<>  feet 
high.  This  dimension  also  allows  the  bottom  of  the  cut  to  be 
so  placet]  that  it  can  be  .-wept  by  the  fire  of  the  demilum 
doubt. 

879..J?  \<  i  -<  •  'vi  i:  m   mi  Hwijon.     PI.  8,  Fig.  3,  and  PL  l. 
Fig.  1.     By  prolonging  the  bastion  counterscarp  to  the  point 
/',  it  serves  a-  a  face-cover  to  the  I  icarp,  masking  it 

frmn  the  fire  of  the  breach  battery  erected  around  the  Balient 
place  of  arme  of  the  demilune  covered-way.  The  angle,./",  of 
the  face-cover  is  placed  on  the  lame  line  as  the  extremity  of 
the  doable  caponniere,  for  the  purpose  of  covering  the  tr» 

ley  debouch  from  the  caponniere,  from  the  enemj 
lishment  along  the  glacii  of  the  bastion   cor<  red-way. 

,ht  of  the  wall,  at  the  point  f\  ii  >"  determined  as  to  inter- 
cept .in  appoint  ■  the 
istioa  covered-way,  and  passing   at   7 


1  38  MOID  i\    mi  i  HOD. 

abovo  the  bottom  of  the  ditch,  at  the  extremity  of  the  capon- 
niere. From  the  point/'',  to  the  gorge  of  the  redoubt  of  the 
reentering  place  of  arms,  the  top  of  the  wall  ascends,  bo  as  to 
cover  the  ramp  Leading  from  the  ditch  to  the  top  of  the  coun- 
terscarp a(  fj ''.  and  also  tlie  passage  leading  from  this  point  to 
the  gorge  of  the  redoubt. 

880... Single  Capototcebi   \m>  Traverse  in    un    Demili 
hii.ii.    Tiiit  last  passage  is  also  covered  from  the  enemy's 

works  on  the  glacis  of   the  demilune  salient    place  of  arms,  by 

the  crest  of  a  single  caponniere,  in  the  ditch  of  the  demilune. 
He  glacis  of  this  work  i>  determined  by  passing  a  plane 
through  the  point,  (83.40),  of  the  interior  crest  of  the  bastion 
face,  found  by  producing  hack  the  demilune  magistral,  and 
through  two  other  points  in  the  demilune  ditch :  one  taken  at 
L3  feel  below  the  ditch  of  the  redoubt  of  the  reentering  place 

Of  arms;    the  other,  at    about    L6.60  feet    below  the    cut   in    the 

demilune.  The  crest  of  the  caponniere  is  held  in  this  plane  j 
and  in  projection,  is  drawn  parallel  to  the  magistral  of  the  face- 

cover,  so  as  to  allow  space  enough  between  it  and  the  foot  of 

the  wall,  which  terminates  the  demilune  face,  for  a  banquette- 

tread  of  2  yards,  and  its  slope  of  l-l  ;  all  of  which  will  require 
about  i.:;m  yards.    The  passage  referred  to  is  4.30  yards  wide. 

In  order  that  it  shall  be  covered  by  the  crest  of  the  caponniere. 
the  bottom  of  it  must  be  at  least  8  feel   below  the  crest. 

381. ..The  preceding  construction  subserves  two  purpoe 

1st,  from  the  position  of  the  glacis  it  is  swept  bv  the  lire  of  the 
bastion  face  ;   30  that  the  dead  space,  which  was  noticed  at  this 

point  of  the  demilune  ditch,  in  Cormontaingne's  method,  is 
here  removed  ;  _d,  it  coven  the  troops  orossiti'g  the  demilune 
ditch  from  the  fire  coming  from  the  demilune  salient  place  of 
arm*. 
382...As  it  is  important  to  keep  this  passage  open,  even  after 

the  enemy  obtains  possession  of  the  demilune,  a  traverse  is 
placed  at  the  extremity  of  the  capoiiiiieiv,  so  as  to  cover  the 
postern  which  communicates  with  the  tcnvplein  of  the  redoubt 
of  the  reentering  place  of  arms.     A  portion  of  this  traverse  has 


NOlZI/bs     Ml    I  lion.  [J9 

to  be  sustained  by  a  wall,  which  is  so  arranged  as  to  afford  tlio 
least  possible  shelter  to  an  enemy,  who.  from  behind  it.  might 
attempt  to  carry  the  redoubt  by  the  gorge. 

383.t.The  fitoe-eover  is  terraced,  the  embankment  being  9<66 
yards  thick  at  top,  and  sloped  inward  toward  the  passage. 

Rbkabk.  The  details  of  this  part  of  the  construction  being 
rather  eomplioated,  will  be  better  understood  by  referring  to 
PI.  L,  Fig.  1,  than  by  any  written  explanation. 

8841..A£a.sx  in  rate  Dimium:  Rjedoi  bt  Dttoh.  PL  4.  Fin.  1. 
To  corer  the  curtain  wall  from  a  fire  through  the  opening  be"* 
twirn  the  flank  and  the  tenaille,  Coming  from  a  battery  estab- 
lished on  the  demilune  terreplein,  an  embankment  is  formed  in 
r  1 1 « ■  ditch  of  the  demilune  redoubt,  tlfee  wall,  which  Bepar 
this  ditch  from  that  of  the  enceinte,  being  bttilt  high  enough 
to  support  the  embankment.  The  embankment  is  sloped  on 
top.  and  terminates  in  a  point  near  the  demilune  cut.  being 
terminated  on  the  side  toward  the  redoubt  by  :i  slope,  the  toot 
of  which  is  fc.80  yards  from  the  foot  of  the  redonbt  scarp.     The 

i<  of  the  embankment  i-  on  the  line  drawn  through  the 
shoulder  angle  of  the  redonbt  and  the  angle  of  the  tenaille. 

38.r»...The  bottom  of  the  ditch  between  the  embankment  and 
redoubt,  is  about    12  feet  abore   that  of  the  enceinte  ditch, 

which  secures  the  demilune  from  being  turned  through  this 
ditch. 

parating  the  embankment  from  the  demilune  re- 
doubt, this  work  b  secured  from  an  attempt  to  carry  it  from 
the  embankment  For  the  same  reason,  the  gorge  wall  behind 
the  cut  b  raised  the  top  .it'  the  embankment     \ 

like  fxp  rted  to  in  all  similar  orge 

wall  of  the  redoubUof  the  reentering  place  of  arms,  and  the 
counter-carp  of  the  demilune  cut.  at  shown  in  the  detail.-  on 
PL  4.  Fig.  1. 

r...<  o\  i  km  i>  u  \«  ~      PI.  5,  Figs.  '•-■    The  bastioned  e 

the   interior  crest    b<  ing   drawn 
illel  to  the  connterecarp. 

arms  are  drs 
17 


13<»  Xnl/.l   l's     Ml    IllOIt. 

parallel  to  the  magistral  of  the  redoubt,  and  -<>  yards  from  it. 
&89.~The  eresl  of  the  demilune  covered-way  is  a  broken 
cremaillere,  or  crotchet  line.  The  short  branches  of  the  ore* 
maillere  are  8.60  yards  Long,  and  are  perpendicular  to  the  di- 
rection  of  the  demilune  capital. 

31'< '.  -.  I  i  i  MASKS'  OB  mi  Ti:  LVEBSE8  AMD  THE  I>1  Ml.i  s.  The  ob- 
jects of  the  short  branches  of  the  crotchets  arc  t<>  cover  the 
dejUes,  or  passages,  between  the  ends  of  the  traverses  and  the 
cri  -t  of  the  covered-way ;  and  to  give  a  column  of  fire  in  the 

direction  of  the  demilune  capital.  To  fulfill  this  last  object, 
the  short  branches  are  provided  with  a  banquette,  with  a  Blope 
of  Only  1-1,  to  bring  the  crest  of  this  branch  as  near  as  practi- 
cable to  the  traverse.  A  passage  of  2.0  yards  is  left  between 
the  foot  of  the  banquette-slope  and  the  wall,  which  terminates 
the  end  of  the  traverse;  the  direction  of  this  wall  is  parallel 
both  to  the  long  and  short  branches  of  the  crotchets,  leaving  a 
passage  between  it  and  the  long  branch.  8.0  yards  wide. 

391. ..To  find  the  position  of  the  short  branch,  the  base  of 
the  interior  slope  being  1.5  feet,  the  bampiette-tread  ti  feet, 
the  base  of  the  banquet te-slope  ',).'>{)  feet,  and  the  width  of  the 

defile  6  feel — IT  feet,  or  5.86  yards,  is  the  entire  distance 
BOUghf  between  the  crest  of  the  short  branch  and  the  wall 
that  terminates  the  traverse  parallel    to  this  branch. 

392. ..The  portion  ot*  the  long  branch,  opposite  the  traverse, 
is  without  a  banquette,  etc..  for  the  purpose  of  leaving  the 
least  distance  between  the  crest  ot'  the  crotchet  and  the  tra- 
verse, so  that  the  defile  may  be  covered  in  the  best  manner. 
To  effect  this,  a  vertical  wall  is  placed  parallel  to  the  end  of 
the  traverse,  and  at  L'.o  yards  from  it,  to  leave  space  for  the  de- 
file ;  this  wall  sustains  the  earth,  but  IS  not  built  up  higher 
than  Within  t.50  feet  of  the  crest.  The. earth  of  the  glacis  has 
the  natural  slope  of  1-1  from  the  crest  to  the  top  of  the  wall  ; 
the  base  of  this  slope,  consequently,  will  be  l..r><i  feet,  and  a 
herm  of  0.60  feet  being  left  on  the  top  of  the  wall.  These 
distances,  together,  give  2.U0  yards  for  the  distance  between 


NOIZKrV    Ml  TI!"I>.  131 

the  crest  of  the  long  branch  ami  the  wall  parallel  to  it,  which 
terminates  the  traverse. 

393...Ti:\\  i BB81  a  OK  mi  ])i  \mi  n1  OoVEBB>WAY.  There  are 
&>nr  traverses  on  the  demilune  covered-way;  which,  to  avoid 
repetitions,  will  be  designated  as  No.  1,  No.  2,  No.  3,  and  No. 
4 — No.  1  being  nearest  the  reentering  place  of  arm.-. 

:::<l...To  construct  the  crotchets  of  traverses  Nos.  1  and  2,  a 
line,  /  in,  is  drawn  parallel  to,  and  at  13.0  yards  from,  the  demi- 
lune counterscarp  ;  parallel  to  this  line,  and  at  a  distance  <>f 
6.60  yards,  measured  on  a  perpendicular  to  the  demilune  capi- 
tal, a  second  line,  /'///.  is  drawn.  The  salient  and  Reentering 
angles  of  the  crotchets,  between  Nos.  1  and  2,  rest- on  these 
two  lines.  * 

395. ..To  construct  traverse  No.  1,  a  line,  n  7i',  is  drawn  par- 
allel to  /'///',  and  at  2.66  yards  ;  from  the  point  of  intersection, 
n,  of  this  line  with  the  cresl  of  the  reentering  place  of  anna, 
a  line,  n  o,  is  drawn,  so  that  its  intersection,  0,  with  the  demi- 
lune counterscarp,  shall  be  perpendicular  to  a  line  drawn  from 
0,  to  the  point '/,  <>n  the  demilune.  The  line  n  o,  is  the  interior 
cresl  of  No.  1.  The  exterior  crest,  n'  o,  is  parallel  to  it,  and 
at  6.66  yards, 

...From  the  point  /''.  a>  a  centre,  with  a  radius  of  5y08 
yards,  an  arc  ia  described  :  a  tangent  drawn  to  this  arc.  pecv 
pendicular  to  the  demilune  capital,  gives  the  short  branch  of 

the  crotchet. 

;...To  construct  traverse  No.  2:  from  the  extremity  of  the 

short  crotchet,  just  found,  with  a  radiu.-  of  6.60  yard>.  an    arc 

i:-  described ;  a  tangent,  drawn  from  the  point  </  t<>  this  arc, 
will  give,  by  its  intersection,  ".  with  the  counterscarp,  a  point 
<»f  the  Interior  crest  ot   No.  -;  the  interior  crest  indrawn  from 
this  point,  perpendicular  to  the  tangent.    The  exterior  o 
Lrawn  at  t  Is  from 

-..To  obtain   the  crotchets  from  any  assumed  point, 
of  th  .  with  radii  of  2.66  and  5.66  yaj 

ribed  ;  tangents  are  'lrawn  to  the*  nun 

the  inner  extremity  of  the  Bhort  branch  of  No.  1  to  the  arc  of 


132  sov/a:i'>  mi:iik>i>. 

2.66  yards,  the  other  to  the  arc  of  5.66  yards,  and  perpendicu- 
lar to  the  demilune  capital,  It  these  two  tangents  interoeot 
on  tlt«-  Line  X  ///.  then  the  point  nl  is  one  point  of  the  end  No. 
i',  and  the  lii**-  /<  //'  is  drawn  parallel  to  the  long  branch  ;  it" 
the  t£  do  not  intersect  on  /'  //<'.  then  some  other  point, 

/<'.  must  be  chosen)  ami  a  .similar  construction  made,  until  tin- 
iiitcjxrtidii  is  found  on  the  line  /"  ///',  which  will  he  the  salient 
angle  <>t  the  crotchets. 

■■'...'I'.,  oenstrttct  No,  3  and  it >  orotchets,  a  point  i.-  taken 
on  thr  .-Imrt  branch  of  (he  crotchet  last  found,  at  4.30  yards 
from  i  t  >  salient  angle;  from  this  point  an  arc  is  described,  with 
a  radius  of  L50  yards;  a  tangent  drawn  to  this  arc  from  tin; 
point  a,  will  give  the  point,  ",  on  the  counterscarp,  where  the 
interior  crest  of  No.  :;  is  to  be  drawn,  perpendicular  t<>  tin-  tan- 
gent.    The  exterior  crest  of  this  traverse  ia  at  L '■'>'■'>  yards  from 

tin-  interior  crest. 

400...The  ahort  branches  of  the  cretcheta-of  No.  8  and  No.  4, 
have  the  same  direction  ai  tin-  others  ;  bat  they  are  limited  by 
two  lines,  one  drawn  parallel  to  the  counterscarp,  and  at  1 i.<> 
yards  from  it,  the  other  at  6.60  yards  from  this,  measured  on  a 
perpendicular  to  the  demilune  capital.  "These  two  lines  being 
drawn,  the  position  of  the  salient  and  reentering  an gleB  of  the 
crofchets  that  rest  upon  them  will  be  found  by  a  construction, 
similar  to  the  one  just  describe^. 

401. ..The  reentering  angle  of  the  crotchet  of  No.  2  ia  cut  oil", 
1»\  drawing  a  line  through  the  centre  of  the  arc,  and  parallel  to 
the  tangent  drawn  to  it  from  a.  , 

402.,/To  construe!  No.  1,  commence  by  finding  the  foot  of 
its  exterior  slope.  Tins  is  done  by  describing  an  arc  from  the 
angular  point,  <■',  of  the  redoubt  df  the  reentering  place  of  arras, 
with  a  radius  of  1.30  yards;  a  tangent  drawn  to  this  arc, 
through  the  demilune  salient,  being  produced  to  the  covered- 

wav,  gives  the  foot  ot' the  exterior  slope.     'Hie  interior  crest  of 

No.  I  is  parallel  to  this  line;  its  position  is  found  by  allowing 

4.66  feet,  or   I..V.  yards,  tor    the  l>;ise  ot    the  exterior  slope,  and 

BO  fret,  or  6.66  yards,  for  the  thickness  of  parapet     Having 


btoqdbt's  mi nK'ii.  L83 

the  exterior  and  interior  crests,  the  point  ?i,  and  the  crotchets, 
a  r<  •  found  as  in  the  preceding  ess 

K)8...The  interior  crest  of  the  salient  place  of  arm.-  is  on  the 
Line,  £  r»>  produced ;  which  ie-at  L  1.0  yards  from  the  counter- 
scarp.     A  pan  soupe*  of  1.80  yards  U  made  in  the  salient. 

4('4...Ti;  w  i  i;-i  on  thi  Bastion  Co*  i m  i>-w  ay.  PL  5,  Pig. 
1.  To  construct  the  traverse1  and  its  crotchets  on  thebaatiqn 
ci,\  iTnl-wav.  a  line,  1  i\  is  drawn  at  6.60  yards,  parallel  bo  the 
crest  of  the  bastion  covered-way :  the  extremity  of  die  trav< 

.  i.-  drawn  parallel  to  /  r,  and  2.60  yards  from  it.  From 
the  point  /'.  <>n  the  crest  of  the  reentering  place  of  arm.-,  the 
interior  crest  of  the  traverse  is  drawn  perpendicular  to  the  baa* 
ti  >n  Counterscarp.  Tin-  exterior  crest  i*  '-'"  ltl  '■  W  ,;-,;,;  yards, 
from  the  interior  creek 

To  find  the  other  branch  of  the  crotchet,  n  n'  is  taken,  equal 
to  5.<»  yards;  a  line  is  drawn  throngh  r  and  //,  and  produced 
to  .v.  on  the  crest  of  the  bastion  eovered-<wajy ;  an  arc,  with  ■ 
radius  of  2.66  yarda,  is  now  described  from  /<'.  and  the  tangent, 
*  l,  drawn  to  this  arc,  is  the  branch  required; 

4<C..(  "mm  \M-  OF  mi:   (  <>\  iKin-w  w  a\i>  Tn.wi  i:h  >.     PL  5, 

Fig.  •_'.  To  arrange  the  relief  of  the  covered-way  and  travel 
tlie  following  method  is  pursued:  The  salient  of  the  demilune 
feet  lower  than  the  salient  of  the  demi- 
lune; the  reference  of  this  point  then  ia  (tO.60).  The  interior 
te  of  the  salient  place  of  arm.-  of  traverse  No.  4.  and  the 
long  branch  between  Noe.  S  and  t.  are  held  in  the  same*pla 
the  icah  which  ia  parallel  to  the  demilune  cap* 

ital ;  its  inclination  being  determined  by  placing  the  extremity 
the  long  branch,  just  referred  to.  0.7;,  feet  lower  than  the 
salient  of  the  demilune  coven 

i  he  short  branch  of  the  ei  -  No*  8  1 

•  red-waj  . 
the  interior  crest  ol  and  the  long  branch,  are  held  in 

the  same  plane,  whoe  In  ity  i-  parallel  to  the  demi- 

lune capita  .  inclination  ii  such  that, 

dated,  it  will  pass  8 


134  N.'l/.l   l'-     Ml  -UK  il). 

4<>7...The  relief  of  No*  -  ;ui<l  its  crotchets  ia  determined  in 
the  BanKB  manner  a>  in  the  preceding  case.  The  reference  el 
the  Bhort  branch  being  fixed  a1  (70.S' 

408.. .The  Balients  of  the  bastion  covered-way,  and  the  re- 
entering place  of  arms,  eommand  the  Balient  of  the  demilune 
covered-way  by  L.50  feet     Their  reference,  therefore,  ie  7 

409. ..Ukmakk.-    09    mi     CoVKBED-WAYS  AND  Ti:.\\i.i;>i>.     The 

demilune  covered-way  is  made  wider  toward  the  reentering,  to 
cover  tlu-  traverse  defiles  with  more  ease.  The  width,  11.0 
yards,  of  the  portion  near  the  salient,  makes  tlif  covered-way 
bo  narrow  that,  should  an  enemy  liml  it  necessary  to  Lower  his 
breach  battery  into  it  to  effect  a  practicable  breach,  he  will  be 
obliged  to  cut  away  a  part  of  the  glacis  to  obtain  sufficient 
room  for  his  works. 

410...The  counterscarp  of  the  redoubt  of  the  reentering 
place  of  arms  is  a  slope  of  earth,  so  as  to  make  the  reentering 
place  of  arms  more  spacious,  by  joining  the  ditch  of  its  terre- 
plein. 

411. ..The  interior  crests  of  the  reentering  place  of  arms  and 
its  two  traverses  are  held  in  the  same  plane,  whose  scale  ofde* 
divitv  is  parallel  to  the  bastion  capital.  This  plane  produced, 
passes  3  feet  above  the  salients  of  the  two  collateral  demilunes* 
from  which  this  place  of  arms  is  thus  defiled. 

412. ..The  crests  <»f  the  bastion  covered-way  are  in  the  same 
plane,  whose  scale  of  declivity  is  parallel  to  the  bastion  capi- 
tal. This  plane,  prolonged,  also  passes  3  feet  above  the  same 
points  as  the  last  mentioned]  and  for  the  same  object. 

ll:;. ..The  traverses  serve  as  masks  to  cover  the  terreplein  of 

the  COVered-way  from  ricochet  shots;    for  this    purpose,  Xos.    li 

and  .*;  may  be  only  4.33  yards,  or  l.">  feet  thick.  Hut  the  other 
traverses,  which  close  the  reentering  and  salient  places  of  arms, 

being  more  important,  have  a  thickness  of  6.66  yards.  As  the 
general  height  of  the  traverses  is  2.66  yards,  it  is  readily  seen 
that,  supposing1  the  extreme  limit  of  ricochet  firing  to  be  an 
angle  of  1-10,  the  traverses  should  not  be  more  than  2b'. (J  yards 


J 


NOTZKl's    MKIIIol).  185 

apart,  in  order  that  a  shot  striking  the  crest  of  one  may  imbed 
Itself  in  that  immediately  in  rear  of  it. 

414.. .The  traverses  also  servo  as  a  defence  :  and  for  this  pur- 
pose arc  made  like  an  ordinary  parapet.  To  enable  the  be- 
sieged to  defend  the  coverediway,  they  are  palisaded,  and 
barriers  arc  placed  at  the  defiles.  As  the  means  of  protracting 
tin-  defence  arc  only  effective  when  the  defiles  .-ire  perfectly 
secured  from  the  tire  of  the  enemy,  established  along  the  Crest 
of  the  salient  place  of  arms,  the  reason  for  the  particular  con* 
•traction  given  for  each  traverse  will  now  be  apparent.  Hie 
interior  crests  of  Nos.  1.  9  and  3  are  so  arranged  that  they 
can  concentrate  their  fire  on  the  salient  place  of  arms  ;  and 
each  traverse  i.-  so  combined  with  the  demilune,  as  effectually 
to  mask  the  defile  of  the  one  in  rear  of  it.  The  defile  of  No. 
1  is  masked  by  No.  -.  and  a  passage  of  about  2.<»  yards  at 
the  foot  of  the  h;ui<jiiette-slo]>e  <  ►  t "  No.   1  is  covered,  so  that  the 

troop.-  can  pass  through  this  defile  in  perfect  safety. 

41 5. ..The  defile  No.  2  is  less  easily  covered  by  No.  3.  To 
effect  it.  the  inner  angle  ot  the  crotchets  has  to  be  cut  off  and 
the  banquette-elope  suppressed,  substituting  in  its  place  Btepe; 
by  these  means,  a  passage  of  l.o  yard  is  •covered,  and  N".  ■'> 

placed  not  too  far  from    No,  -. 

416...  As  it  is  hot  practicable  to  cover  the  defile  of  No.  8,  the 

tion  of  No.  i  18  determined.  BO  a-  to  make  the  salient 
place  of  arms  a-  spacious  CM  possible.      This  is  done  by  phi 

4  in  a  position,  to  allow  its  exterior  slope  to  be  swept  by 
the  fire  of  the  bastion  face,  penetrating  between  the  salient  of 
the  demilune  and  the  angle  of  the  redoubt  of  the  reentering 
place  of  arms. 

41 7. ..The  defile  of  the  traverse  on  the  bastion  covered-way, 
nt  any  line  of  fire  penetrating  through  it 
Into  the  reentering  place  of  arm?. 

418.. .The   precautions  which  arc   here    taken  would    1" 
insufficient,  could  the  enemy,  in  possession  of  tin  f  the 

salient  place  of  arm-.  ha\  e  a  plui  red- 

•rmy  behind  the  trav<  I-     -  to  prevent  tin's  that  th< 


13H  Nol/.i •■["-    KKTHOD. 

terior  crests  of  the  different  traverses  and  their  respective 
crotchets  are  held  in  the  same  plane  J  which  is  bo  arranged 
thai  the  terreplein  shall  be  defiled  from  the  enemy's  lodgment 

on  the  crest  of  the  salient  phu f  arms.     Tin's  arrangement 

necessarily  places  the  terreplein  between  the  traverses  on  dif- 
ferent level.-;  small  ramps  will,  therefore,  be  necess.arv  to  ; 
from  one,  level  t«>  the  other.    They  are  placed  at  the  defiles. 

41  '.♦. ..The  salient  ]>laee  of  arms  is  inclined  for  the  purpose  of 
partially  defiling  it  from  the  trench  cavalier. 

420.. .Finally,  tic  traverses  are  sustained  on  the  Bide  of  the 
counterscarp  by  I  profile  wall,  which  is  the  prolongation  of 
the  counterscarp  wall;  and  they  are  terminated  at  the  other 
extremity  by  a  wall,  so  as  to  make  the  defile  convenient  a>  a 
communication. 

421. ..Coi'ntikx  u;rs  i>i- Tin;  Bastion  am>  Demilcxtb.  Hav- 
ing determined  the  relief  of  the  covered-way  crests,  which,  it 

may  lie  observed,  is  such  that,  they  mask  all  the  masonry  Of 
the  scarps,  and,  at   the  same   time,  are   BO    low  that    an    ciicmy 

cammt.  by  the  ordinary  methods  in  use,  obtain  a  plunging  tire 

from  them  dpOU  the  terrc|>lcins  of  the  works  in  their   rear,  the 

position  of  the  counterscarp  carestB  can  now  he  fixed. 

I  •_'•_'. ..The  top  of  the  counterscarp  wall  should  he  at    least  8' 
h-ct  below  the  planes  of  the  interior  creal  of  the  covered-way, 

and  the  height  of  the  wall  for  the  body  of  the  place  should  not 
exceed  24  feet,  and  for  the  demilune  it  may  be  reduced  to  18 

feet.  Tin  .-e  dimensions  will,  therefore,  be  assumed,  as  the 
greatest  that  can  he  allowed  with  a  proper  regard  to  economy. 
And  a  continuous  wall  of  these  heights  may  be  regarded  a-  a 

powerful  auxiliary  obstacle,  in  securing  the  works  from  all 
attempts  at  surprise. 

■12:;. ..Adopting  the  limit  of  24  feet  for  the  counterscarp  of 
the  bastion,  it  will  be  seen  that  the  bottom  of  the  ditch  at  the 

toot  of  this  wall  is  higher  than  at  the  foot  of  the  scarp  wall  of 
the  bastion  face;  and,  as  the  bottom  of  the  ditch,  at  the  ex- 
tremity of  the  double  caponniere,  has  already   been  determined, 


noizkt's  method.  137 

these  different  levels  must  be, connected  by  planes,  combined* 
in  the  most  simple  manner, 

•|-_'  !...<    i  M  li  I  -    LND  BOTTOMS  OF  THE    DrTOHES.       PI.-.  4  Mini  .'.. 

A  dinette,  4.<>  yards  wide  at  top,  and  3  feet  deep,  is'  made  in 
the  main  ditch  to  serve  as  a  drain.  A  cvJUoert,  or  small  arch 
of  masonry,  is  made  under  the  double  caponniere,  connecting 
the  cunette  on  the  opposing  .-ides  of  it.  The  cunette  ifl  placed 
parallel  to  the  bastion  face;  tin-  bottom  of  the  ditch  having  a 
slope  of  1.50  feci  from  the  foot  of  the  scarp  wall  to  the  edge  of 
the  cunette,  and  a  slope  from  the  opposite  edge  up  to  the  foot, 
of  the  counterscarp  wall.  These  details  will  he  hest  under- 
stood by  referring  to  I *].->.  4.  5,  Figs.  1.  The  slopes  hefre  given 
-erve  to  keep  the  bottom  of  the  ditch  dry;  they  a— i-t  in  ren- 
dering  the  breach,  made  in  the  bastion  face-,  rather  Btei 
than  if  the  bottom  were  horizontal :  and,  in  the  passage  of  the 
ditch,  the  enemy's  work  i-  thus  more  exposed  than  if  the  bot- 
tom were  not  sloped  from  the  foot  of  the  counterscarp  wall  to 

the  cunette. 

The  demilune  ditch  is  arranged  upon  similar  principles.    A 

cunette  and  culvert  are  placed  in  it.,  to  convey  the  rainwater 
froyi  it  into  the  main  ditch. 

4_'.V..I'l.\\i  -  OF  THE  G  The  glacis  of  the  covered-way 

may  now  he  considered.  <  hie  principle  is  chiefly  to  be  attended 
to  in  disposing  the  different  planes  of  the  glacis.  They  should 
all  he  swept  by  the  artillery  tire  of  the  works  immediately  in 
their  rear,  and   by   the  niu.-k«  try  lire,  at    least,  of  the   bastion 

-iL'''>...The  glacis  of  the  bastion  coverecUway  should  lie  swept, 
by  the  artillery  of  the  bastion  fa< 

1-7.  .The  glacie  of  the  re<  ntering  place  of  anas  should  he 
swept  by  the  tire  from  it-  redoubt. 

4l"v    I       j  the  demilune  "tier,-  more  difficulty  in  its 

arrange  ment,  owing  to  the  cremaillece  form  of  the  interior 

l>e-t    method   seems    the   following :   plat 
passed  t  as    to    1 

artiUerj  demilun<  . 

1- 


13S  Noi/.i  r'a  mi  thod. 

are  connected  by  another  Beries  of  planes,  which  are  pas 
through  the  salient  point  <»t"  cadi  crotchet  below  the  plane  of 
musketry  fire,  of  at   Least  one-half  of  the  bastion  tare;  and 
below  thai  <>f  artillery  fire, jrf  a  part  of  the  demilune  tare. 

4 :.".'... It  will  he  readily  seen,  from  the  nature  of  this  prob- 
lem, that  it  admits  of  many  solutions.  In  selecting  amoi 
them,  the  following  considerations  may  serve  a.-  guides.  Wlien 
the  planes  of  the  glacis  have  a  very  gentle  slope,  they  are  bet- 
ter seen  by  the  works  in  their  rear;  but  the  construction  is 
more  expensive,  on  account  of  the  greater  quantity  of  em- 
bankment. 

430... When  the  slope  is  more  steep,  the  enemy's  works  on 
the  glacifl  are  better  exposed  to  the  reverse  views  of  the  collat- 
eral works,  although  not  so  well  seen  by  those  directly  in  rear 
of  the  glacis;  but  the  quantity  of  embankment  is  smaller. 

431...0tTLi;rs,  ok  Soktii:  Passages.  To  communicate  from 
the  covered-way  with  the  glacis,  an  <>utht  or  80fii<  poesOffi  is 
cut  in  the  least  exposed  face  of  the  reentering  place  of  arms; 
and  one,  also,  on  the  long  branch,  between  the  3d  and  4th 
traverses.  They  are  from  8.30  to  4.0  yards  wide.  The  cut  is 
about  6  feet  in  depth,  the  earth  being  sustained  on  each  side 
by  a  protile  wall.  The  bottom  of  it  is  a  ramp  leading  from 
the  terrepleiu  of  the  c. Aercd-way  to  the  top  of  the  glacis.  A- 
the  outlet  is  closed  by  a  barrier,  it  should  be  arranged  at  the 
bottom,  to  alloW  tin-  barrier  free  play  in  opening  ami  shutting, 

432...CoMMr.Mi'ATi"\>.  There  is  no  part  of  a  fortification 
where  more  care  and  judgment  are  required  than  in  the  dis- 
positions made  to  communicate  from  tin-  interior  with  the  out- 
works. The  safety  of  the  besieged  essentially  depends  on  a 
proper  disposition  of  the  communications,  which  should  afford 
vwvy  facility  for  offensive  movements,  and,  at  the  same  time, 
a  Beeute  and  easy  means  ot  retreat.  This  subject  has  been 
treated  with  peculiar  care  by  Noi/.et. 

b'l.'b.. Besides  the  ramps,  which  have  already  been  explained, 
DOSteraB  and  stairs  form  a  part  of  the  system  of  communica- 
tion. 


noizkt's  method.  139 

434.. .Posterns,  as  already  lias  been  stated,  arc  arched  com* 
mnnicatione  of  masonry,  made  under  the  rampart  or  terreplein. 
When  these  communications  are  required  for  the  passage  of 
artillery,  they  Bhould  be  at  least  lo  feet  wide,  and  8  feet  high 
under///-  crown  ot  hey  of  tfu  arch.  When  for  infantry,  they 
may  be  reduced  to  1  feet  in  width,  and  6 feet  in  height,  under 
the  key.  The  arch  of  the  postern  is  generally  a  semi-circle, 
<>r  what  is  called  a  full  centre  arcA.  i&  be  bomb-proof ,  it 
should  be  at  least  3  feet  thick  through  the  masonry  of  the  arch, 
«ind  be  covered  by  at  least  from  8  to  £.60  feet  of  earth. 

135. ..Stairs  are  only  used  in  situations  where  ramps  cannot 
be  placed :  as  for  example,  to  communicate  with  the  interior 
of  works,  the  gorges  of  which  are  revetted. 

Cacti  step  is  generally  formed  of  a  single  block  of  stone, 
which  is  2.0  yards  long  m  to*  dear\Q.Z0  yard  in  width,  and 
0.20  yard  high.  Prom  these  dimensions  of  the  height,  or  i 
and  width,  or  tread,  of  each  step,  we  obtain  the  following  for- 
mula for  the  hase  of  &  flight  of steps ',  when  the  height  between 
the  two  landings  is  idven,  8-2  //  —  <». 30  =  1) ase. 

Stairs  are  not  so  convenient  as  ramps  J  and  they  are,  more- 
over, liable  to  be  easily  put  out  of  order  by  the  effects  of  shot 
and  shells. 

}.',o...(  ,  .mmi'nk   \!io\   OF  Tin     EnCT  in  i  i"  ■  wi  'in    THE     iMou. — 

The  postern  of  the  enceinte  lead.-  through  the  middle  of  the 
curtain,  descending  from  the  plane  of  sight  to  the  ditch.  The 
inclination  of  the  bottom  should  never  exceed  1-6.  The  bot- 
tom should  not  corns  out  upon  I  Level  with  the  bottom  of  the 
ditch,  l>ut  about  6  feet  above  it — a  wooden  ramp  being  need  to 
end  from  the  postern  to  the  bottom  of  the  ditch, 

The  width  of  thifl  postern  should  be  1_  feet,  both  bn  account 
oft  ter  circulation  through  it,  and   because  it  may  he 

;  as  a  bomb-proof  shelter  for  the  troops  on  duty. 

I  to  this  postern,  both  toward  the  ditch  and  the 

interior,  is  by  door-ways ;  one  through  the  scarp  wall,  which 
closes  the   postern   toward  the  ditch,  and  one  through  a 
tical  wall  ol  ty  of  the  enceinte  b 


140  noizet's  method. 

plein,  which  closes  the  month  of  the  postern  toward  the  inte- 
rior. The  earth  of  the  rampart-slope  is  cut  away,  to  leave  the 
passage  t"  the  postern  free.  The  sides  of  the  cut  are  sustained 
by  wing  walls,  which  make  a  small  angle  with  the  vertical  Wall 
of  the  postern  mouth.  The  door-way  may  be  7.0  feet  wide, 
ami  7.50  feel  high.  The  postern  itself  being  1"  feet  under  the 
bey. 

For  more  security,  a  partition  wall,  with  a  «1 '-way,  is  some- 
times made  across  the  postern,  about  the  middle  point.  The 
leaves  of  the  folding-doors  here  have  loop-holes  to  fire  upon  an 
enemy,  should  he, by  asurprise,  gain  possession  of  the  exterior 
door-way. 

437...Co\|Ml  NI.'ATIo.N      Willi      1  I!  I :    Tl  N  A I  I.I.K.        A      postern,    for 

the  passage  of  artillery,  is  made  under  the  teuaille,  and  leads 
to  the  double  caponniere.  Two  stairs  are  placed  at  the  gorge 
of  the  tenaille,  to  communicate  with  its  berreplein. 

438...G'MMr.\i<  ation     with    nii:    Ti  i;i;i  i-i.i.in    and   Diivii   Qg 

Tin;  Demilune  RwJoubt,    Two  stairs  are  placed  at   tlie^orge 

of  the  demilune  redoubt,  to  communicate  with    it*   terrcplein. 
A  postern  for   artillery  leads  from  the   main  ditch  to   the  ditch 
of  the  redoubt, under  it8  flank,  for  the  communication  between 
the  main  ditch  and  the  demilune. 
439...Co.M.Mi  mi  \ii<>\    1K0M   mi;   Enceinte  Ditch  with  nut 

ExTEBIOB.  To  communicate  with  the  covered-ways,  a  ramp  of 
earth  sustained  by  walls  i>  placed  along  the  wall  that  termi- 
nates the  demilune  and  its  redoubt.  This  ramp  is  separated 
from  the  extremity  of  the  face-cover  by  a  cut  4.30  yards  wide. 
•1  !<»...(  'ommimca  iio.n  wnii  mi:  DEMILUNE  Gut.  The  com- 
munication with  the  work  behind  the  demilune  cut  is  by  a 
postern  and  Stairs  for  infantry,  which  lead   from  a  point  on  the 

ramp  just  described  to  the  terreplein  of  the  work — passing  in 

a  winding  direction  under  the  tcrreplcin  and  parapet  of  the 
work. 

441...Commi  mi  ai ions  of  the  Redoubt  01  the  Ki:-i  mi  kim. 
Place  of  Asms,  etc  The  passage  behind  the  single  capon- 
niere. in  the  demilune  ditch,  has  already  been  described.    The 


NOIZETS    METHOD.  14  I 

passage  leads  to  a  postern  for  artillery,  made  through  the  face 
of  the  redoubt,  to  its  ditch.  From  the  ditch,  a  ramp  for  ar- 
tillery Ira. Is  to  the  terreplein  of  the  reentering  place  of  arms. 
At  the  angle  of  the  redoubt  on  the  demilune  ditch,  stairs  are 
placed  to  ascend  to  its  ditch;  a  ramp  for  infantry  leads  from 
the  ditch  on  this  side  to  the  terreplein. 

44l'...To  ascend   to  the  terreplein  of  the  redoubt,  a  small 

bern    for   infantry  is  made  through   the  face  to  the   ditch. 

being  placed  alongside  the  postern  just  described ;  from  this, 

a  winding  postern  and  stairs  lead  to  the  terreplein   of  the  re- 

doubt. 

Hie  foregoing,  with  what  has  been  said  respecting  the  ca- 
ponnieresj  traverse  defiles,  etc.,  completes  the  description  of 
the  communications  of  the  front.  This  subject  may  l.e  closed 
with  a  recapitulation  of  the  principal  conditions  wlu'ch  should 
regulate  every  system  of  communications. 

44.".... Ki  m.\i;k>  om  im.  Communications.  1st.  Tfn  commu- 
nication* should  ?"  n  their  position^  compromise  tJu 
safety  ofthi  <  run  ink  . 

frequent  i i i.-l a l ic< 's  ceul d  he  cited  of  works  which  have  been 
surprised  by  an  enemy  obtaining  possession  of  the  gates. 
Therefore!  too  many  precautions  cannot  be  taken  to  secure  the 
principal  outlet  from  the  body  of  the  place  from  similar  at- 
tempt.-. It  is  on  this  account  that  the  postern  in  the  body  of 
the  place  is  arranged  as  has  been  described,  to  frustrate  any 
indden  attack  that  might  be  made  upon  it. 

i  l  b..L'd.  77/.  communications  should  admit  of  a  oonv*  nu  tU 

ibserve  this  purpose,  the  dim*  •<•..  of  the 

posterns,  ramps,  and  other  similar  works,  should  be  convenient 

for  I  •  which  they  are  app  I  they  should    be 

placed  in  such   j  directly  to  the   poii 

arrived  at     In  «  namii  "  >rra,  dim  :ion 

the  front,  it  will  be  found  that  th 
ditions  s 

4  15.. .3d.    7 /<<  positi 


142  noket's  method. 

why  that  when  cm  enetny  gets  possession  of  it.  In  may  ob- 
tain ik'  advantagt  by  it. 

To  be  useless  to  an  enemy,  the  communication,  when  in  his 
poggi  ssion,  should  nol  ofFer  a  shelter  for  his  works;  nor  enable 
liini  to  carry  them  on  with  more  ease.  Tins  end  will  be  ob- 
tained by  placing  the  communications  in  a  position  to  be  en- 
filaded by  the  fire  of  the  works  in  their  rear;  and  so  arranging 
them  as  to  preserve  the  counterscarp  wall  unbroken,  by  which 
means  any  facility  for  attempts  at  surprise  will  be  avoided. 

4th.  The  communications  should  bt  covered  from  every  point 
when  an  enemy  might  establish  himself,  during  th<  whole 
peribd  thai  they  oun  h  of  service  to  tin  besiegers;  and  they 
should  be  swept  by  th>  firs  of  thi  <  n<-<  info  . 

Without  these  precautions,  an  enemy  might  cnt  oil'  all  com- 
munication from  the  enceinte  with  the  outworks;  and  in  cases 
of  retreat,  the  troops  could  not  derive  any  assistance  from  the 
enceinte,  if  he  attempted  to  press  upon  them. 

446.. .In  covering  the  communications,  existing  masses  should, 
when  convenient,  be  used,  which  form  a  part  of  the  general 
arrangement  of  the  works.  Examples  of  this  are  shown  in  the 
manner  in  which  the  debouohS  from  the  double  caponniere, 
and  also  those  from  the  traverse  defilesj  are  covered.  In  the 
firsl  case,  by  the  angle  of  the  counterscarp  wall  and  the  salient 
of  the  bastion';  and  in  the  second,  by  the  angle  of  the  profile 
walls  of  the  traverses  and  the  demilune  salient.  Sometimes  a 
special  mask  has  to  be  raised,  an  example  of  which  is  seen  in 
the  traverse  at  the  gorge  of  the  red6ubt  of  the  reentering  place 
ofarra8,  which  covers  the  door  of  the  postern  of  the  redoubt. 

•1  I7..."'th.  The  communications  should  fo  so  placed  as  hot  to 
compromise  tlu  retreat  of  th  troops. 

This  is  effected  by  placing  the  communication  in  the  ree*n- 

terlngS,   Which    are    the    most   secure    points,   a>    an    enemy   to 

arrive  at  them  will  have  to  brave  a  powerful  column  of  flank 
lire.  Barriers,  gates,  and  movable  bridges  of  timber  should 
be  placed  at  Buitable    points,  to  cut  off  one  communication 


NOI/.I  t's  method.  143 

from  another;  ami  thus  arrest  the  progress  of  a  pursuing 
enemy. 

448...6th.  Finally,  each  work  should  <«  independent  qf  every 
cotflmunicatioti,  except  thi  <>n'  destined  for  Us  particular  use. 

This  is  ;m  important  object,  as  it  prevents  an  enemy,  should 
lie  succeed  in  gaining  possession  of  a  communication  leading 
through  it.  from  seizing  upon  tlie  work  itself.  Examples  of 
this  arrangement  arc  shown  in  the  postern,  through  the  face 
of  the  redoubt  of  the  reentering  place  of  arms,  which  leads  i" 
the  exterior,  and  which  is  not  connected  with  the  small  postern 
destined  for  the  service  of  the  redoubt  itself;  also,  in  the 
postern  leading  from  the  main  ditch  to  that  of  the  demilune 
redoubt,  for  the  service  of  the  demilune.    This  postern  does 

not  interfere  with  the  safety  of  the  redoubt. 

-M'.'...r.\  examining  the  communications  of  the  front,  gen- 
erally, according  to  these  conditions,  it  will  he  found  that  their 
arrangement  i:-  a.-  judicious  a-  the  nature  of  the  problem 
seems  to  admit. 

■l.'.n... In -,,  ,;,,,,;    Ri  11:1  n<  iimi  vis.     The  front,  as   it    has  now 
been  described,  appears  to  be  of  a  character  to  protract  the 
■    to  the  longest   duration.     When,  however,  a  breach  is 
made  in  the  enceinte,  although  military  usage  and  a  point  of 
honor  require  of  the  garrison  to  sustain,  at  least,  one  assault, 
the  consequences  of  defeat  are  of  too  serious  a  character  to  ex- 
•   such  an  effort,  unless  a  place  of  safety  i>  provided,  into 
which  the  garrison  may  retreat,  after  defending  the  breach, 
and  obtain  an  honorable  capitulation.     <h\  this  account,  and 
to  lengthen  the  defence,  interior  retrenchments  tax  made 
in  the  bastions.     These  works  may  he  either  of  a  temporary  or 
permanent  character;  hut  i;  led  that  the 

latter  class  alone  off  tele  to  t: 

former,  mor»  !  it  the  bi  ould  be  full, 

that  the  retrenchment  Bhottld  be  thrown  up  during 
an  nndertaki  lifficulty,  both  from  tl 

the  enemy's  lire  and  tie   I 
ordinary  dut 


1-1:4  NOD5BT8   HBIHOD. 

451. ..Therefore,  only  the  permanent  interior  retrenchments 
with  a  revetted  Bcarp  and  counterscarp  will  be  given  :  and 
which  may  be  regarded  as  an  element  of  a  regularly  fortified 

front. 

•1 .",_'.. .Xoizet,  like  Cormontaingne,  proposesfour  classes  of  in- 
terior retrenchments.  1st.  Those  thai  rest  against  the  faces  of 
the  bastions.  2d.  Those  that  rest  against  the  flanks.  3d. 
Those  that  rest  against  two  adjacent  curtains.  4th.  Those  that 
comprehend  several  bastions. 

•!."•:'.. ..Fiust  CLA88    RESTING  ON    Till:    FACES.      PI.  G,    Fig8.    1.    -, 

and  .1.  />.  Fig.  3.    The  first  class  may  be  either  the  form  of  a 

cavalier,  shut  in  by  cuts  across  the  bastion  faces,  or  an  inverted 
redan  ;  or,  finally,  if  the  bastion  is  very  open,  a  small  bastion 
front.  Of  this  class,  the  cavalier  has  been  generally  employed. 
The  cavalier  receiving  a  relief  so  great  as  to  give  it  a  plunging 
fire  upon  the  enemy's  works  on  the  glacis  of  the  bastidned  cov- 
ered-way ;  whilst  the  interior  of  the  bastion,  in  advance  of  the 
cavalier  ditch  and  of  the  cuts  or  ditches  across  the  bastion  tcr- 
replein,  between  the  scarps  of  the  bastion  and  cavalier,  is 
swept,  and  the  breach  that  might  be  made  in  the  bastion 
salient  can  be  defended  from  the  parapets  behind  the  cuts. 
These  parapets,  with  the  portions  of  the  cavalier  faces  in  ad- 
vance of  them-,  forming  the  interior  retrenchment. 

1. vi. ..This  class  presents  the  advantages  of  defending  the 
breach  within  a  short  distance,  and  by  enclosing  the  thinks  of 
tli.'  bastion  within  them,  they  preserve  the  thinking  arrange- 
ments of  the  body  of  the  place  until  the  retrenchment  is  car- 
ried. The  principal  objection  to  them  is  that,  by  a  breach 
made  at  lite  shotllder  angle,  the  enemy  can  turn  them. 

45  5... Second class  besting  AjGAINST  the  Planes.  PI.  6,  Figs. 
4  and  C.  The  second  class  may  be  of  an  inverted  redan,  or  a 
small  bastion  front;  or,  finally,  of  a  redan  resting  against  the 
middle  of  the  flanks,  its  faces  having  such  a  direction  that  its 
ditch  maybe  swept  by  the  fire  of  the  flanks  of  the  adjacent 

l>a.-tions.   . 
The  last  form  admits  of  defending  the  breach  within  a  short 


noi/.kt's   METHOD.  145 

distance;  it  preserves  also  the  flanking  arrangements  of  the 
enceinte,  and  can  only  be  turned  by  a  breach  made  id  the  cur- 
tain. To  sweep  its  ditch  from  the  opposite  Hank,  it  will  be 
neog&sary  to  cut  down  a  pari  of  the  scarp  wall  of  the  flank  on 
which  the  ditch  rests^  which  will  make  the  height  of  the  wall 
less  than  11.0  yard.-,  and  somewhat  expose  the  enceinte  to 
escalade. 

1  .■"><!. ..Tmiti>  ei.\--  BESTEN&  ON  5PW0  aim  \<  r.\  i  ( 'i  i;i wins.  PI. 
6,  Fig.  4.  I>.  The  third  class  is  usually  of  the  form  of  a  has- 
tened front  ;  but  as  the  tire  of  its-faces  would  be  masked  by 
the  curtain  of  the  enceinte,  it  is  generally  beet  to  construct  the 
front  simply  with  a  curtain  and  two  flanks. 

Thi.-  class  being  thrown  farther  from  the  salient  of  the  bas- 
tion, does  not  defend  the  breach  so  directly  as  the  two  preced- 
ing; but  its  position  i>  stronger,  and  will  force  an  enemy  to 
employ  more  means  t<-  carry  it.  From  its  djmensions,  it  will 
require  more  space  on  the  interior,  and  will  he  also  more  ex- 
pensive than  either  of  the  preceding  tonus. 

4r»7...Foi  inn  <i.\—  i  mi.o-im,  >i.vi.i;.\i.  Fbohts.  The  fourth 
clas-,  which  is  placed  in  the  rear  of  .-evoral  hastions  of  the  en- 
ceinte, or  properly,  several  fronts,  [e  a  kind  of  sec. . ml  enceinte 

within  tiie  ftrat.     An  arrangement  of  this  character  would,  of 
course,  require  a  peculiar  locality,  and  would  seldom  find   an 
application. 
458... <  \ •>  •. i .ii  i;  wiiu  Oon   i.\  mi    Bjjstios   F.\<  i -.     I'l.  6, 
s.  1,  2.    The  -  work  are  parallel  to  those  of  the 

bastion  in  which  it  is  placed  ;  its  ditch  should  be  about  L8  feet 
>w  the  bastion  terreplein  :  it.-  scarp  wall  about  l'4  feet  high. 
And  it  may  be   I  d  that  ali  interior  retrenchnu 

to  ope  -  oa  obstacle  to  an  enemy,  should  bav< 

ments  of  about  these  dimensii 

'4.'. '.'...The  interior  crest  of  I  bould  be  so  high  that  the 

line  of  fire,  from  the  salient  of  the  cavalier  to  the  salient  of  the 

bs^tion  rn\,  red-way,  shall  pas.-  above  the  bastion  salient.      I'.v 

the  counterscarp  ol  the  cavalier  at  L4.0  yards  from  the 

interior  crest  of  the  bi  allowing  L1.0  vard-  for  the  width 

19 


146  Noi/.l  !*-    Mi  THOD. 

of  tin-  ditch,  and  making  the  bottom  of  the  ditch  18  feet  In-low 
the  bastion  terreplein— it  will  be  found  that  the  reference  fitf 
the  bottom  of  the  ditch  will  be  (58.50);  the  scarp  wall  being 
et  high,  the  reference  of  its  magistral  be  (82.50).  Now, 
if  the  reference  of  the  interior  crest  be  taken  at  (97.50),  or  15 
feel  above  the  magistral,  its  projection  will  be  at  33.16  feet,  or 
11.Q6  yard.-  from  the  magistral :  and  as  both  the  lines  arc  hor- 
izontal, parallel  to  it.  Drawing,  then,  three  lines  parallel  to 
the  bastion  interior  crest,  at  the  distance  above  mentioned,  the 
projections  of  the  counterscarp,  scarp  and  interior  crest  of  the 
cavalier  are  obtained.  The  position  here  given  to  the  interior 
crest  of  the  face  will  satisfy  the  condition  first  laid  down. 

40<>. ..The  interior  crest  of  the  think  Is  also  horizontal-;  its 
reference,  therefore,  is  ((.i7.">,,i ;  the  direction  of  the  Hank  14 
perpendicular  to  the  line  of  defence  of  the  bastion  ;  the  think, 
moreover,  is  not.  revetted  like  the  face,  but  is  terminated  by 
prolonging  its  exterior  slope  to  thenastion  terreplein  ;  the  low- 
est point  of  the  foot  of  this  exterior  slope  will,  therefore,  he 

about  (T-':.(,iM,  the  reference  of  the  hastioii  terreplein  at  the  ex- 
tremity of  its  flank;  the  least  width  of  the  bastion  terreplein, 
between  ItB  think  and  that  of  the  cavalier,  should  be  14.0  yards. 
If,  then,  from  the  interior  angle  Of  the  curtain,  with  a  radius  of 
14.0  yards,  atn  arc  be  desoribed,  and  a  tangent  be  drawn  to  this 
arc,  perpendicular  to  the  line  of  defence,  this  tangent  may  he 
taken  as  the  horizontal  of  the  exterior  slope  of  the  cavalier 
flank,  whose  reference  is  (73.0) ;  the  interior  crest  of  the  flank 
is  drawn  parallel  to  this  horizontal,  and  at  41.10  feet,  or  L8/f$ 
vanU  from  it  ;  which  will  be  the  distance  found  by  calculation, 
the  thickness  of  the  parapet  being  20  feet,  the  superior  slope 
I-*;,  and  the  exterior  .-lope  1-1. 

-lol...The  lengtb  of  the  flank  is  found  by  drawing,  through 
the  angle  of  the  curtain,  a  line  parallel  to  the  line  of  defence  ; 
and  where  it  cut.-  the  interior  crest- of  the  Hank,  will  be  the 
extremity  of  the  Hank.  • 

1ol'...To  terminate  the  gorge  of  the  cavalier,  a  plane  of  1-1  is  # 
passed  through  the   extreme  points  of  the   interior  crest  of  its 


noizkt's  method.  ]47 

flanks.  A  passage  of  4.30  v;inls  is  left  on  the  bastion  tenre- 
plein/at  the  gorge  of  the  cavalier,  to  communicate  with  it; 
and  also  to  preserve  an  uninterrupted  communication1  between 

flic  two  adjacent  curtains.  A  ramp,  3.30  yards  wide,  with  a 
slope  of  1-6,  leads  from  the  gorge  of  the  cavalier  to  its  tcnv- 
plein.  This  ramp  is  generally  placed  along  the  capital  of  the 
bastion. 

(«!3...CrTs  t.n  the  Bastion  Fa<  k>.  PI.  0,  FigB.  1.  -.  To  de- 
termine  the  cut  across  the  bastion  face,  a  distance  of  13.0  yards 
is  set  off  from  the  shoulder  angle  of  the  bastion,  along  its  inte- 
rior crest;  from  this  point  a  line  is  drawn,  making  an  angle  of 
]on°  with  the  interior  crest ;  this  line  being  produced  to  inter- 
sect the  magistral  of  the  cavalier  face,  is  the  interior  crest  of 
the  parapet  behind  the  cut.  The  reference  of  this  line  where 
it  intersects  the  magistral  is  (8*2.50),  the  reference  of  the  other 
extremity  being  (84.0) ;  it  is  held  in  the  same  plane  with  the. 
portion  of  the  interior  crest  of  the  hastion.  between  the' shoulder 
angle  and  the  point  at  13.fi  yards  from  it;  the  reference  of  the 
shoulder  angle  remaining  as  already  found;  it  will  he  seen 
that  the  plane  of  these  two  lines  produced,  passes  3  feet  above 
tlie  bastion  salient.     The  thickness  of  parapet  is  only  \'l  feet. 

4&4k..The  magistral  of  the  scarp  of  the  cut  is  horizontal. 
reference  being  70;5O  .  From  the  preceding  data,  its  | 
tion  i.s  easily  determined.  A  line  drawn  parallel  to  the  magis- 
tral, and  at  6.60  yard-  from  it.  will  he  the  counterscarp  of  the 
cut.  The  counterscarp  wall  of  the  cut  i>  carried  up  to  the  top 
of  the  bastion  face,  and  forms  a  profile  wall  to  sustain  the 
earth.     The  scarp  wall  of  the  cut  is  of  the  same  height  as  that 

of  the  cavalier;  the  bottom  of  tin-  cut  will,  therefore,  be  n 
speed  (52.60),  a  portion  of  the  ditch  of  tfrc  cavalier  face  has 
the  same  reference:  thia  portion  is  found  by  holding  at  the 
.  that  part  of  the  bottom  of  the  ditch  toward  the 
salient  which  can  be  swept  by  the  tire  of  the  parapet  behind 
the  cut;  placing  the  bottom  of  the  remaining  portion  toward 
tin-  cut,  on  the  same  level  as  the  bottom  of  the  cut,  or  at  the, 


1  t8  NOIZET'fl    METHOD. 

reference  (52.50);  the  two  levels  being  separated  by  a  vertical 

wall  <">  feet  high,  which  retains  the  earth  of  the  tipper  level. 
465.. .This  arrangement  of  the  ditch  of  the  cavalier  subject! 

only  a  part  of  it  to  the  tire  of  the  parapet  behind  the  cut.      By 

placing  the  door  of  the  postern  that  leads  into  the  cavalier 
ditch,  at  the  point  where  the  vertical  wall  separates  the  two 
levels,  it  will  he  partially  covered  from  the  enemy's  lodgment 
on  the  bastion  terreplein. 

4nV,...The  object  of  the  cut  is  similar  to  the  one  in  the  demi- 
lune face;  it  confines  the  enemy  to  the  salient  part  of  the  bas- 
tion, preventing  him  from  extending  his  works  along  the 
bastion  terreplehi,  to  turn  the  cavalier  by  its  gorge*;  so  that  to 
obtain  possession  of  this  work,  he  must  make  a  breach  in  its 
face. 

ln'7... There  is  a  dead  space  in  the  cavalier  ditch  throughout 
the  lowet  level,  which  might  offer  some  advantages  were. the 
enemy  to  attempt  to  carry  the  parapet  of  the  cut  by  escalade. 
To  remedy  thi>  defect,  it  has  heeii  proposed  to  place  a  cremated 
gallery  behind  the  scarp  wall  of  the  (ait,  to  flank  the  entire 
ditch. 

468. ..The  disposition  of  tho»cavalier  and  cuts  within  the  has- 
tion  do  not  leave  sufficient  space  upon  the  terreplein  of  the 
latter  to  organize  a  covered-way.  But  in  the  retrenchments  of 
open  hastions,  resting  on  the  flanks  or  curtains,  to  which  the 
form  of  a  tenaille,  or  a  small  hastioncd  front  is  given,  a  cov- 
ered-way, with  a  reentering  place  of  arms,  closed  by  traverses, 
can  he  organized,  which  will  give  considerable  additional  coriJ 
lideiice  and  security  in  the  defence  of  the  broach  in  the  bastion 
with  the  bayonet— as  this  covered-way  will  cover  the  retreat 
of  the  troops,  guaruing  the  breach,  into  the  ditch  of  the  en- 
ceinte—whereas, when  the  counterscarp  is  not    secured    in  this 

way,  the  retreating  body  run  the  risk  either" of  being  cut  off  or 

of  having  the  enemy  follow  so  closely  on  their  heels  as  to  force 

their  way  into  the  retrenchment,  and  deprive  the  defence  of 
.this  last  resort  for  making  favorable  terms  of  surrender.       » 
469. ..The  organization  of  these   covered-ways  presents  no 


; 

CHA88ELOUP  8    METHOD.  14-9 

peculiarity.    They  should,  as  far  as  practicabley'be  defiled  from 
the  besieger's  lodgments  with  the  bastion  assailed. 


CHASSELOUFS  METHOD. 


+7<)...Ohasse1onp  was  one  of  the  most  distinguished  engineers 
under  Napoleon,  aTid  had  the  principal  charge  of  the  fortifica- 
tions constructed  by  tHe  French  in  the  north  of  Italy,  whilst  it 
was  i  pari  of  the  French  empire.  His  views  are  to  be  gath- 
ered chiefly  from  some  short  memoirs  published  without  his 
name,  in  which  are  to  he  found  many  of  the  Leading  ideas  of 
pal  later  engineers  of  the  French  school,  and  what  is  now 
termed  the  German  school. 

4?l...Chasse)oap  adheres  to  the  bastioned  system  as  the 
basis  of  his  enceinte,  in  which,  however,  he  proposes  the  fol- 
lowing modifications  of  the  combinations  usually  admitted  by 
his  predecessors,  viz:  1st,  in  giving  a  greater  Length  to  the  ex- 
terior side,  which  he  p/oposes  to  vary,  if  necessary,  bet* 
440  and  660  yards;  2d,  in  so  arranging  the  plau  of  his  en- 
ceinte that  the  portion  of  the  bastion  faces  toward  the  salients 
shall  be  covered  by  the  demilunes  from  enfilading  views:  3d, 
in  throwing  hack  the  parapets  of  cerURn  portions  of  his  front, 
which  are  exposed  to  be  breached, so  far  to  the  rear  that  when 
the  scarp  wall  is  battered  down  the  breacfl  will  still  be  cl 
by  the  parapet :  4th,  in  arranging  the  tenaille  wit)  sted 

flanks  solely  for  ditch  defencej  which  !   by  a  n 

from  the  counter-batteries  at  the  salient  of  the  bastioned  • 
ered-way;  whilst  by  openings  pierced  in  the  mask,  the  lii 
the  think-  can  be  din  ctcd  on  the  point  to  be  attained  •  5th,  in 
placing  in  the  main  ditch  a  caseraated  caponniers  t.»  obta 


150  :  "i  r"-   mi  ["HOD. 

iwi'M'  fire  on  the  breaches  in  the  bastion  faces;  6th, in  isolat- 
ing the  main  ditch  from  the  ditches  of  the  outsorts,  covering 
it  and  the  caponniere  by  a  covered-way,  organized  with  case- 
mated  traverses  and  redoubts  for  defence;  Tth,  in  detaching 
the  demilune  from  the  enceinte,  throwing  it  bo  far  forward  as 
to  cover  the  bastion  faces  from  enfilade,  and  in  placing  in  tlio 
demilune  a  casemated  redoubl  to  procure  reverse  views  on  the 
approaches  on*  the  bastion  salient.-;  8th,  in  organizing  the 
demilune  covered-way  in  the  same  manner  as  that  of  the  en- 
ceinte; 9tb»  in i  placing  within  his  bastions  strong  interior  re- 
trenchments, with  casemated  skelters  for  the  artillery  in 
reserve,  and  defensive  casemated  quarters  for  the  garrison* 

47l\  Plan.  The  exterior  side,  PL  IT,  X  Y,  is  taken  at  580 
metres  I  French);  the  perpendicular,  Z  U,  is  $  of  X  V;  a  por- 
tion of  each  face.  A'///.  Ym\  equal  to  60m., lies  on  X  )':  from 
in  and  ////  lines  of  defence  are  drawn  through  U,  on  which  the 
interior  portions  of  the  faces,  each  1  ( W >  in. ,  are  set  otf;  the 
flanks  are  drawn  perpendicular  to  the  lines  of  defence,  and  are 
about  48  in. 

-173. ..The  tenaillc  is  separated  from  the  curtain  by  a  ditch 
of  1"  in.,  and  from  the  thinks  by  ditches  of  L5m.  The  rear 
portion  <•.  Figs.  1,  %  of  the  flank,  is  casemated  tor  three  guns, 
each  casemate  being  open  to  the  rear;  an  open  court.  <.  of'  a 
rectangular  shape,  is  left  opposite  the#casemates,  in  front  of 
which  is  the  mask,  </,  pierced  with  arched  openings,  through 
which  the  shot  from  the  casemated  guns  are  directed.  The 
gorge  of  the  tenaillc  has  a  counterscarp  gallery. 

474. ..The  salient,  #,  of  the  capoiinic»e  in    the    main   ditch   is 

at  55  m.  from  Z,  on  the  exterior  side  ;  its  faces,  .v.  /•'.  are  65  m., 

and  directed  on  points  Qi  (/,  at  5(1  m.  from  tin-  bastion  shoul- 
der  angles  ;  the  flanks  are  parallel  to  the  perpendicular  of  the 
front,  and  60w.  The  parapets  of  this  caponniere  are  thrown 
hack  from  the  scarp  wall  to  increase  the  difficulty  of  the  breach  J 
the  parapets  of  the  faces  being  higher  than  those  of  the  thinks, 
to  cover  them  from  enfilade  \iews.  The  masonry  of  the  thinks 
of  this  work   is  covered  by  a  glacis  y  zf,  which   is  revetted, 


CHASSELOtrr'a  method,  151 

leaving  ditches  of  5  m.  between  it  atfd  the  scar])  and  counter- 
scarp of  the  enceinte,  and  of  10  in.  between  it  and  the  0&pon> 
nieiv  flank.-. 

47-b..The  counterscarp  6f  the  main  ditch  is  20m.  wide  at 
the  salients,  ami  directed  on  the  flanks  of  the  capouniere  at 
points  5  in.  from  the  shoulder  angles.  The  ditch  qf  the  capon* 
nieiv  at  the  faces  is  Id  m.  wide. 

47n\..The  covered-way  lias  a  reentering  place  <>f  arms  at  the 
reentering  between  the  counterscarps  of  the  enceinte  and  ca- 
ponniere  feces,  which  extends  to  within  50m.  of  the  front  S\ 
A  salient  place  of  arms,  of  a  polygonal  form,  like  that  of  the 
demilune  cvend-way.  hut  not  represented  on  Fig.  1,  is  ar- 
ranged in  front  ot  each  ha-tioned  salient.  Each  of  these 
places  of  arms,  Figi  4,  is  odcupied  with  a  polygonal  easemated 
redoubt.  Tin1  branches  <»f  tin1  covered-way.  between  the 
places  of  arms,  are  broken  into  a  ere maillere  line,  the  longer 
branches  of  which,  prolonged,  fall  within  the  bastion  salients. 
Tra\  mated  fiif  reverse  fires  or  of  the  ordinary 

traction,  are  place/1  in  the  enlarged  portions  of  the  cov- 
ered-way formed  by  the  Ion--  and  short  branches  of  the  ere- 
maillere.  The  directions  of  the  crests  of  the  covered-way,  and 
their  lengths,  are  given  by  the  dimensions  on  the  plan. 

•177. ..Tiie  salient,  J\  ot'  the  demilune,  is  at  17<un.  from  the: 

point  8',  on  the  ca]>oiini7re  countei>ear|>  ;   its  faces  are  direct. d 

on  points j?//,  at  LOO  a.  from  the  bastion  shoulder  angles.  A 
cut  of  .'.in.  is  made  in  each  face  of  this  work  at  7<Un.  from 
the  salient.  The  faces  are  prolonged  60  m.  beyond  the  cut, 
and  are  terminated  l.v  arcs  described  from  the  shoulder  ai  i 
the  demilune  redoubt  and  lines  drawn  from  these  centr 
points  on  tin-  bastion  capitals,  at  40  tn.  in  advance  of  the  salient 
place  of  arms.  Within  the  salient  of  the  demilune  a  cure  1 
traverse  is  arranged,  with  conntersloping  emh  for  how*- 

it/er  firing  along  the  capitals,  in  rear  of  which  18  a  small  . 
d  redoubt,  /.'.      Tin-  demilune  ditch  is  iOttl.  v, 

478. ..The  ditches  of  the  demilune  redoubt,  Is  m. 

wid.  >f  this  work  are  '-V1  in.:   its  flank-.  '_'"  m. 


1  •"'•_'  <  ii  \  — n."i  p'fl   mii  mmi>. 

flank.-.  Fig.  ."..  are  casentated  for  -  guns.  The  gorge  of  the  re- 
doubt is  a  .- m t ; 1 1 1  bastioned  front.  The  faces  and  flanks  have  aa 
.open  defence  covered  by  a  parap<  t. 

47,.'...Thc  demilune  covered-way  is  organised  Like  that  of  the 

inte,  with  casemated  redoubts,  A',  />''.  in  the  salient  and 

reentering  places  of  anus.     Between   these'  redoubts  are  two 

traverses,  «  A,  <t  ///  the  latter  cover*  the  masonry  of  the  re* 

doubt,  J',  and  doses  the  reentering  places  of  arms. 

480.. .The  glacis  of  the  enceinte  slopes  off  toward  the  gorga 
of  the  demilune  and  its  redoubt,  So  thai  all  the  rear  of  these 
wbrks  is  exposed  t<»  the  face  of  the  enceinte. 

481... Besides   the   ordinary  open  communications,  Chas 
roup's  front  is  organised  with  a  »erj  extrusive  combination  <>f 
posterns  and  galleries  for  scarp  and  counterscarp  defences  and 
mines,  both  for  the  Bervice  of  the  defences  of  the  enceinte  and 
of  the  outworks. 

£68...The  principal  features  of  Ghasseloup's  combination^ 
consist  in  liis  mode  of  olosfng  the  opening  for  breaching  the 

bastion  faces,  as  scciitin  X'anhan's  fronts,,  through  the  demilune 

ditches,  by  throwing  forward  the  demilune  as  a  detached 
work  :  in  his  organisation  of  his  covered-ways  with  casemated 
redoubts,  and  oi  his  demilune  re'donbt  with  casemated  flanks 
having  reverse  views  on  the  bastion  glacis;  It  has  been  ob- 
jected to  the  position  he  gives  the  demilune  that  both  this 
Work  and  its  covered-way  are  exposed  to  be  carried  1>\  an 
open  assault  at  the  gor^e,  in  which  case  its  redoubt  would 
readily  fall,  and  the  advantages  proposed  be  lost;  also,  that 
the  casemated  redoubts  in  the  eoveredrways  will  be  so 
damaged  by  the  ricochel  fire  of  the  enfilading  batteries  as  to 
be  useless  when  the  covered-way  is  attacked. 


HAXOV    METHOD.  153 


HAXO'S  METHOD. 


483.. .General  ETaxo  holds  the  first  rank  among  the  more  r& 
cent  engineers  of  the  French  b61ioo1.  Having  served  under 
Chasseloup  in  tlie  construction  of  the  fortifications  of  Northern 
Italy,  he'  subsequently  acquired  a  distinguished  reputation  by 
hie  services  in  the  Peninsular  war,  whore  he  was  engaged  in 
seven]  of  the  remarkable  sieges  of  that  epoch,  and  he  finally 
became  President  of  the  Board  of  Engineers,  and  in  that  capa- 
city directed  several  of  the  most  important  fortifications  of 
I  <latc  in  •France. 
Nothing  of  General  Haxo's  views  on  the  subject  of  fortifica- 
tion came  before  the  public  during  his  life.  The  front  which 
■•companies  this  description  he  had  engraved.)  &nd  copies  of 
it  distributed  among  the  officers  of  his  corps,  but  under  an  in- 
junction of  Becrecy. 

•im...TYan.    Tire  sxterior>Bide,  0  1h  of  the  enceinte, "PI.  18, 

'.:.lv  yard-:  the  lines  of  defence,  C  //.  D  6?,  arc  directed 

On  the  point  />'.  at   18.T2  yards  from  (".  or  one-ninth  of  the 

i  the  fa<      '     E  and  />  F\  are  7l.-"._!  yard-:  tin 

flanks  I:  <  > .  /-  If.  are  perpendicular  to  the  lines  of  defence. 

|$5...The  tenaille  consists  of  a  em-tain  and  flans 
revetted  only  on  the  exterior  of  the  two  flanks;  it  is  separated 
from  the  curtain  <>f  th<>  enceinte  by  a  ditch  18.11  yards  wide, 
and  fn»m  the  flanks  by  one  of  6.6U  yard.-:  the  Hank-  of  the 
tenaille  are  abonl  8  feet  higher  than  its  curtain,  and  an  ar- 
.-■•d  for  three  guns.     The  lout  of  the  exterior  the 

tenaille   em:  sch   side  the 

h  ;it  wall    Of  the  Hank    0< 
nn  rices. 
20 


154  HAXo'e    METHOD. 

486..,Gounterguards  are  placed  in  front  of  the  bastions;  the 
(fitches  between  them  and  the  bastions  Ik-mi-:  1»>.;'.0  yards  wide 
at  the  salient,  and  their  counterscarps  being  directed  on  a  point 
J >" .  38.25  yards  from  ( " ;  the  salients  of  the  countergaarda  are 
on  the  line  -I  B,  parallel  to  C  IK  and  {!»  yards  from  it:  the 
faces  A  A".  5  .'/.  are  138.81  yards,  and  parallel  to  the  coun- 
terscarps  directed  on  />",  which  form  the  gorge  walls  of  the 
connterguards ;  the  flanks  A*/..  .'/  .V.  an-  perpendicular  to 
the  exterior  side,  and  are  terminated  on  a  line  parallel  to  it 
through  the  shoulder  angles  of  the  bastjon& 

lv7...An  elbow  cut,  5.46  yards  wide,  is  made  across  the 
counterguaxds  at  84.16  yards  from  the  salient ;  the  portion  of 
the  counterguard  behind  the  cut  is  arranged  for  cannon.  The 
ditches  of  the  connterguards  are  21.86  yards  wide  at  the  aa* 
lients;  the  counterscarps  are  directed  upon  a  point,  0'\  at 
ISM  yards  from  C". 

&88~.A  casemated  eaponniere  is  placed  in  advance  of  the 
connterguards,  the  middle  of  its  gorge  being  on  the  line,  A  B, 
joining  the  salients  of  the  counterguatds,  and  its  salient,  P,  at 
t03.83  yards  from  O  /  Its  feces,  /',  JJ\  are  29.51  yards  !•  »ntr, 
and  directed  on  points  at  5.  16  yards  from  the  shoulder  angles, 
A'..)/,  of  the  connterguards;  its  flanks,  TJ\  V,  are  36.07  yards 
long,  and  perpendicular  to  the  exterior  side. 

489..iTo  construct  the  demilune,  points  .)/",  .)/'"  are  taken  on 
tin-  bastion  faces  at  13.58  yards  from  the  Bhouider  angle,  and 
on  the  line  joining  them  an  equilateral  triangle  is  formed,  the 
vertex  of  which,  .//,  is  the  salient  of  the  demilune,  and  the  two 
sides'    the   directions   of  the   faces,    // -s',  //   7\  which    are    Id 

yards  long.     An  elbow  cut,  5.46  yards  wide,  is  made  on  eaob 
face  at  l'Gd.8  yards  from  the  salient  7/,  and  separates  the  por> 

tion  -/  from  the  salient. 

Intl.. .The  salient,  Q,  of  the  demilune  redoubt  is  55  yards  from 
the  salieat,  J\  of  the  eaponniere;  its  faces,  Q,  U,  are  parallel 
to  those  of  the  demilune,  and  65.58  yards  long.  The  iianks, 
U  V,  X  J",  are  parallel  to  the  capital,  and  terminated  on 
lines,  x  x',  drawn  from  ,t-  on  the  counterscarp  of  the  redoubt  to 


HAX0  8   METHOD.  1  *'."> 

%'  on  the  line  A  /?,  tit  6.56  yards  from  tlic  flanks  of  the  capon* 
mere. 

l'.»l...Tlie  counterscarps  of  the  counterguards,  from  the  points 
»".  <"',  on  the  prolonged  faces  of  the  demilune,  arc  directed  on 
points  <m  the  flanks  of  the  caponlriere,  at  L0.93  yards  fffem 
their  extremities,  to  points  /',  al  13.11  yards  from  these  flanks; 
and  from  f  they  are  broken  parallel  to  the  flanks,  and  con- 
tinned  to  g  on  the  line  x  ri. 

492...A  casemated  redoubt  is  placed  lb  each  reentering  place 
of  arms;  its  face,  b  <\  is  directed  on  a  point,  /.  at  36.07  yards 
from  «",  and  is  39.35  yards  lone;:   the  other  face,  h  £,  is  perpen- 

dicular  to  b  c,  and  21.66  yards  loner. 

493.. .A  casemated  redoabt  is  also  placed  in  the  salient  place 
of  arms  of  the  demilune  eovered-way.  Tlie  covered-way  and 
thetreentering  places  of  arms  are  arranged  in  the  usual  manner 
for  sorties,  and  with  trav.  i 

■41*1. ..Interior  retrenchments  are  arranged  in  the  bastions. 
Tn  the  one  on  the  right,  the  parapet  of  the  flank  is  broken  to 
increase  the  amount  of  flank  tire.  In  the  one  on  the  left,  a 
high  cavalier  is  placed,  having  one  tier  of  Casemated  tire,  with 
earthen  embrasures  flke  those  already  described,  and  which. 

from  their  having* been  introduced  by  Ha\o.  are  known  as  the 

Elaxo  casemate,  with  an  upper  tier  of  uncovered  fire. 

The  ditcher-  of  thi  Dohments  are  swept  t'rom  the  oppO- 

■.'... .1 1  ;i\< >  cas<  mat  -  are  placed  in  the  salients  of  the  eottnv 
terguards  and  the  salient  of  the  demilune. 

1'.H;...'l'he    portions  of  the  curtain   parapet   of  tl nceinte, 

near  the  curtain  j  ire  retired  to  give  a  more  effective  dl- 

tion  to  the  guns  on  these  portions,  and  t..  lengthen  the  par- 

the  flanl 
407... The  oommunicatiou  from  |  ate  to  the  main  ditch 

is  by  s  postern  under  the  curtain.    The  communications  with 
the  count  rguardi  and  other  outworks  are  through  the  ditch. 
between  the  flanks  of  tb< 
inunlcatiou  in  trout  of  th<  fa  tiaille  hem-  by  the  i 


156  IIAXo's     MITIIOD. 

I,  I  of  the  glacis  in  front  of  it,  and  by  the  traverse  B,  and  that 
across  the  main  ditch  to  the  main  caponniere  by  the  double 
caponniere  A'. 

498. ..The  ramps,  stairs  and  other  passages  leading  to  the 
tenrepleins  of  the  different  works  are  indicated  Oil  the  plan, 
and  are  so  placed  as  to  satisfy  the  conditions  laid  down  for 
these  important  elements  of  a  front. 

499. ..The  plane  of  comparison  to  which  the  plan  is  referred 
is  taken  at  60  feet  below  the  plane  of  site.  The  relative  com* 
mand  and  the  relief  of  the  enceinte  and  other  component  parts 
are  thus  easily  deduced  ;  and  it  will  be  seen  that  every  ad- 
vanced part  is  well  swept  by  the  fire  of  the  more  retired  parts. 

500. ..From  an  examination  of  the  plan,  it  will  be  further 
apparent  that,  by  the  position  and  length  given  to  the  faces  and 
flanks  of  the  bastions,  the  former  arc  less  exposed  to  eniila4ing 
views,  and  the  lire  of  the  latter  is  considerably  increased,  as 
compared  with  Cormontaingne's  method  and  the  subsequent 
modifications  of  it ;  this  increase  in  the  number  of  guns  that 
may  be  brought  to  bear  on  the  positions  of  the  besieger  is  far- 
ther increased  by  the  flanks  of  the  tenaille,  those  of  the  coun- 
terguards,  and  the  flanks  of  the  cavalier? 

501. ..The  counterguards,  with  the  tenaille,  mask  completely 
the  scarp  of  the  enceinte  from  any  position  that  the  besieger's 
batteries  can  occupy  beyond  the  main  ditch.  All  the  out- 
works exterior  to  the  counterguards  are  well  swept  and  flanked 
by  the  lire  of  the  latter. 

502. ..The  batteries  of  the  flanks  of  the  casemated  caponniere 
sweep  effectively  every  point  in  advance  of  them,  and  see  in 
reverse  the  breaches  that  can  be  made  in  the  counterguards. 
The  scarp  of  this  work,  as  well  as  that  of  the  counterguards,  is 
masked  by  the  plan  and  relief  given  to  the  counterscarp  of  the 
main  ditch  and  the  covering  masses  of  earth  behind  it,  from 
the  besieger's  batteries  on  the  crests  of  the  bastion  and  demi- 
lune salient  places  of  arms. 

503. ..The  demilune,  from  its  salient  position,  has  strong  re- 
verse views,  upon  the  glacis  in  advance  of  the  salients  of  the 


CHOUMARA  S    METHOD.  157 

enceinte,  from  the  casematcd  battery  in  its  salient ;  whilst  the 
mass  of  this  battery  serves  as  a  traverse  to  cover  the  portions 
of  the  faces  in  rear  of  it  from  enfilading  fire.  The  demilune 
redoubt  serves  the  usual  purpose  of  this  work;  its  flank  is 
casematcd.  « 

604... Although  not  clearly  indicated  on  the  plan,  the  para- 
pets of  those  portions  oY  the  works  exposed  to  be  breached  are 
thrown  back  from  the  scarp  wall,  and  a  chemin  de  ronde  is 
firmed  at  the  foot  of  the  parapet.  By  this  disposition,  a 
breach,  when  made,  will  be  more  difficult  of  assault;  the  re- 
tired position  of  the  parapet  will  be  less  exposed  to  ricochet 
fire,  and  the  ch< miit  cU  ronde  will  afford  both  greater  security 
from  surprise  and  a  good  position  for  sharp-shooters  against  the 
trenches. 

505. ..It  is  estimated  that,  by  allowing  the  usual  progress  of 
the  besieger's  approaches,  Haxo's  front  will  recpiire  about  50 
days  for  its  reduction.  The  besiegers,  besides  the  ordinary 
trenches,  batteries  and  descents,  will  have  to  resort  to  at  least 
five  epochs  of  breaching  batteries:  lit,  for  opening  the  demi- 
lune and  the  redoubt  of  the  salient  place  of  arms  ;  2d,  against 
the  demilune  redoubt,  the  portion  of  the  demilune  in  rear  of 
the  cut,  and  the  redoubt  of  the  reentering  place  of  arms  ;  3d, 
against  the  counterguards  and  the  casematcd  caponnicre  ;  4th, 
against  the  bastion  faces  ;  and,  5th,  against  the  interior  re- 
trenchments. 


CHOl'MARA'S    METHOD. 


50f>...Choumara.a  French  officer  of  engineers,  of  distinguished 
abilities,  is  the  author  of  several  remarkable  memoir*  on  the 


158  CIlnlM  \K  \">    MIT!Io]>. 

defects  of  tlio  bastioned  system,  and  tlie  moans  by  which  they 
may  be  removed, and  verygceal  additional  strength  lie  thereby 
given  to   the  defences.      IIi>  propositions  for   this    purposo 

may  lie  briefly  stated  as  follows  : 

507.. .1st.  That  part  of  iB  permanent  work  which  can  un- 
dergp  no  modification  during  the  progress  of  a  siege  is  the 
masonry,  and  it  may,  therefore,  be  regarded  as  the  really  per- 
manent feature;  all  the  parts  of  earth,  as  the  parapets,  etc., 
being  snsceptible  of  snob  modifications  as  circumstances  may 
demand. 

This  Choumara  terms  the  independence  of  the  parapets  as 
respects  the  scarps.  This  latter,  upon  which  the  security  of 
the  work  against  an  open  assault  or  a  surprise  depends,  must 
necessarily  receive  a  direction,  such  that  it  can  be  swept  by 
the  flanking  arrangements,  a  necessity  that  does  not  exist  for 
the  parapets,  which  may  receive  any  direction  compatible  with 
the  interior  space. 

The  parapets  may,  therefore,  be  thrown  back  from  the 
salients,  as  in  the  bastion,  PI.  19,  Fig.  1,  and  receive  a  cur- 
vilinear form  to  throw  a  greater  volume  of  fire  in  the  direction 
of  the  capital ;  or  they  can  be  retired  from  the  faces,  as  in  the 
bastion,  Fig.  A,  for  the  purpose  of  giving  them  such  direc- 
tions that  their  prolongations  shall  cut  the  adjacent  demilunes, 
and  thus  be  masked  from  enfilading  views;  or  they  may  be 
prolonged  so  as  to  afford  a  greater  column  of  flank  fire,  as  in 
the  flanks  7,  Fig.  1 ;  or  they  may  be  broken  into  any  direc- 
tion for  the  same  purpose,  or  to  give  a  more  effective  direction 
to  their  tire;  or,  finally,  they  may  be  thrown  back  from  the 
scarp  walls  instead  of  resting  immediately  upon  them,  and 
thus  render  a  breach  less  practicable,  since  the  wh.ole,  or  a 
portion  of  the  parapet,  will  still  retain  its  place  after  the 
breach  has  been  made  in  the  scarp — depending  on  the  dis- 
tance at  which  the  parapet  has  been  moved  back.  In  all  of 
these  cases  of  the  application  of  the  independence  of  the  para- 
llels, Choumara  proposes  to  convert  the  space  left  between  the 
foot  of  the  parapet  and  the  scarp  wall  into  a  chemin  de  ronde, 


choumaea's  Mi/iiKin.  159 

or  corridor,  which  is  covered  in  front  by  a  slight  parapet,  and 
from  enfilading  fire,  by  a  bonnet  of  suitable  height  at  the 
salients,  as  in  Figs.  1,  A,  B,  etc.  This  corridor  is  occupied  by 
sharp-shooters,  to  annoy  the  besieger's  trenches.  Further- 
more, Choumara  regards  the  corridor  as  an  additional  security 
against  surprise  and  escalade. 

508. ..2d.  Choumara  proposes  to  place  high  traverses  in  the 
bastion  salients,  to  cover  the  faces  from  enfilade,  and  the 
flanks  from  reverse  views;  and  similar  traverses  at  the 
shoulder  angles,  with  the  same  object.  These  he  also  pro- 
poses to  casemate,  or  else  construct  with  blindages  for  artillery 
to  obtain  a  lire  in  the  directions  of  the  capitals,  and  reverse 
views  on  the  demilune  glacis  and  the  breach  in  the  bastion 
face.  As  these  traverses,  from  their  height,  might  give  the 
besiegers  in  possession  of  them  a  plunging  fire  on  the  bastion 
retrenchments,  Choumara  proposes  so  to  arrange  them  that 
they  can  be  readily  destroyed  at  any  moment  by  mines,  or,  if 
of  timber,  be  burned. 

509.. .3d.  To  mask  the  masonry  of  the  enceinte  and  demi- 
lune from  breaching  batteries,  erected  in  their  usual  positions 
along  the  crests  of  the  glacis,  Choumara  proposes  to  form  what 
he  terms  an  interior  glacis,  or  covering  mass  of  tarth,  in  the 
ditches,  the  crests  of  which  shall  mask  the  masonry  of  the 
scarps  from  the  positions  in  question.;  and  the  upper  surface  of 
which,  forming  a  glacis,  shall  be  swept  by  the  fire  of  the  works 
in  its  rear.  In  this  manner,  Choumara  proposes  to  force  the 
b<  siegers  to  the  difficult  operation  of  making  lodgments  in  this 
sis,  to  obtain  suitable  positions  for  their  breaching  batteries. 

.Mo...  }th.  Choumara  proposes,  by  a  judicious  selection  of 
positions  for  some  of  the  outworks,  to  occupy  those  positions 
on  the  exterior  whidi  are  most  favorable  to  the  sharp-shooters 
of  the  besiegers,  and  thus  cripple  this  important  arm  of  the 
attack. 

511.. .6th.     By  giving  gi  tent  to  the  exterior  side,  and 

a  more  retired  position  to  the  curtain,  which  is  also  to  be  mads 
as  short  as  possible,!  houmara  proposes  to  obtain  bastioi 


L60  CHOUMARA  S    METHOD. 

ample  size,  not  only,  to  admit  of  the  modifications  he  proposes 
for  the  parapets,  traverses  and  ckemwts  de  ronde,  but  for  strong 
interior  retrenchments,  so  organized  with  bomb-proof  ■shelters, 
ami  arranged  defensively  toward  the  interior,  that  each  bas- 
tion will  admit  of  a  defence  to  the  rear  at  its  gorge,  after  the 
besiegers  may  have  effected  a  breach  at  other  points,  and 
penetrated  within  the  enceinte. 

512. ..Plan.  In  adapting  these  propositions  to  a  bastioned 
front,  Choumara  proposes,  in  order  to  obtain  the  requisite  room 
in  the  interior  of  the  bastions  and  a  large  increase  of  flank  fire, 
to  take  the  exterior  side  from  400  to  600  metres,  French.  In 
the  front,  Fig.  1,  PI.  19,  for  example,  the  exterior  side  is  440 
metres ;  the  lines  of  defence  are  drawu  through  a  point  on  the 
perpendicular  of  the  front  at  74  m.,  or  1-6  of  440  in.  within 
the  exterior  side  ;  the  faces  are  150  m.,  and  the  flanks,  drawn 
perpendicular  to  the  lines  of  defence,  are  85  m. — a  length 
which  prolongs  them  35  m.  within  their  intersections  with  the 
lines  of  defence.  By  this  construction,  the  curtain,  which  will 
be  115  m.  long,  will  be  well  swept,  and  the  gun  at  the  curtain 
angle  can  be  brought  to  bear  on  the  one  of  the  besieger's  coun- 
'ter-battery  against  the  flanks  which  are  furthest  out,  thus  giv- 
ing a  very  great  preponderance  in  fire  to  the  flank  over  the 
counter-battery. 

513.. .The  deep  reentering  thus  formed  between  the  flanks 
and  curtains,  gives  ample  room  for  a  tenaille  with  flanks  for 
four  guns  ;  these  guns  are  covered  in  flank  by  a  traverse.  The 
tenaille  is  not  revetted  in  front  of  its  curtain  and  flanks,  or  at 
its  gorge.  Tt  masks  sufficiently  the  scarp  of  the  flanks  and 
curtain  of  the  enceinte,  to  prevent  any  danger  to  the  latter 
from  the  destruction  of  the  portion  of  the  scarp  wall  tnat  can 
be  seen  over  the  tenaille. 

514.. .The  salient  of  the  demilune  is  the  vertex  of  an  equi- 
lateral triangle,  the  base  of  which  is  drawn  between  two  points 
on  the  bastion,  faces,  at  18  m.  from  the  shoulder' angles.  The 
faces  of  the  demilune,  D,  are  144  metres,  and  revetted.  The 
parapet  of  the  demilune  is  thrown  back  from  the  revetement, 


choumaka's  method.  161 

leaving  a  corridor  covered  by  a  parapet  at  tlie  foot  of  its  ex- 
terior slope.  The  parapet  is  broken  near  the  gorge,  so  as  to 
give  two  short  flanks  of  13  m.  perpendicular  to  the  exterior 
side.  The  salient  is  occupied  by  a  easeniated  traverse  with 
flanks  for  three  guns.  This  traverse  masks  the  interior  of  the 
demilune  and  the  Corridor  from  enfilading  views.  A  disposi- 
tion is  shown  for  cuts  across  the  demilune  faees,  the  parapets 
of  which  are  to  he  thrown  up  after  the  siege  commences.  The 
demilune  ditch  is  IT  m.  wide.  The  portion  of  this  ditch 
toward  the  gorge  slopes  upward  as  a  glacis,  and  is  swept  by 
the  fire  of  the  enceinte. 

515. ..The  interior  glacis  of  the  demilune  commences  at  the 
counterscarp  of  this  work,  and  has  a  glacis-slope  outward,  its 
width  being  15  m.  Here  commences  the  revetted  gorge  of 
the  covered-way.  The  width  of  the  covered-way  is  10  m.  Its 
interior  crest  is  an  indented  line.  There  are  no  traverses  in 
this  work,  unless  required  for  its  defilement; 

516...  A  spacious  and  strong  redoubt  is  placed  in  the  demi- 
lune salient  place  of  arms.  Its  faces  are  132?m.  long,  and  re* 
vetted.  Its  parapet  is  thrown  back,  leaving  a  corridor  in 
front  of  it,  and  is  curved  at  the  salient  for  live  guns,  sweeping 
along  the  capital.  A  bonnet  is  placed  in  its  salient  to  cover 
the  corridor  from  enfilade,  and  two  traverses  for  the  same  ob- 
ject on  its  terreplein.  This  redoubt  forms  a  mask  for  the  por- 
tion of  the  demilune  occupied  by  the  traverse. 

517...C'homnara  places  strong  redoubts,  jf,  with  revetted 
scarps  and  gorges  in  the  reentering  place  of  arms.  The  para- 
pets  of  these  works  are  curved  at  the  salients  for  batteries  to 
Bweepthe  approaches  on  the  bastion  capitals  and  tie-  demilune 
glacis,  and  they  are  thrown  back  from  the  scarp  walls  to  give 
a  corridor  for  sharp-shooters.  As  these  redoubts  are  n< 
sarily  contracted,  Choumayi  prefers  {o  them  a  strong  redoubt 
of  larger  dimensions,  placed  in  the  bastion  salient  plac* 
arms,  and  organized  like  tin 

5 18.. .One  of  the  most  striking  features  of  ChoumaiVa  modi- 
fication-., ie  the  mode  in  which  he  proposes  to  organize  the 
21 


162  CHOUMAKa's    MKIIImI). 

• 

large  bastions,  with  defences  which  shall  s*crve  as  an  interior 
retrenchment  in  ease  the  bastion  is  one  of  the  points  of  attack  J 
or  convert  the  bastion  into  an  isolated  fort,  or  citadel,  for  the 
garrison,  in  ease  the  besieger  gains  possession  of  the  interior 
of  tha  enceinte  through  an  assault.  This  he  proposes  to  ac- 
complish, b y  increasing  the  lengths  of  the  exterior  side,  and' 
also  of  the  bastion  Hanks. 

519. ..With  this  object,  Chouinara  places  a  row  of  easeinates 
within  the  bastions,  on  a  line  perpendicular  to  their  capitals; 
Each  casemate  is  from  60  to  80  feet  long,  from  12  to  20  feet 
wide,  and  12  feet  high.  This  row  of  casemates  serves  as  a 
curtain  both  for  the  retrenchment  of  the  bastion  and  for  the 
defence  of  the  gorge  against  an  interior  attack.  For  the  de- 
fence of  the  salient  portion  of  the  bastion,  a  cut  is  made  across 
each  face  and  extended  to  the  capital.  The  scarp  of  this  cut 
is  made  into  the  form  of  a  bastion  front  with  orillons  at  the 
shoulder  angles ;  the  casemates  forming  the  curtain  of  this 
front.  The  eounterscarp  of  the  cut  may  be  either  revetted  or 
have  a  simple  slf>pe  of  earth.  In  the  latter  case,  the  bottom 
of  the  ditch  of  the  front  at  the  foot  of  the  scarp  wall  is  at  a 
suitable  level  to  admit  of  a  suitable  height  of  scarp  wall  to 
secure  it  from  escalade.  A  broad  ramp  leads  from  the,  centre 
casemate,  along  the  capital  toward  the  bastion  salient,  to  the 
counterscarp  of  the  cut,  and  there  branches  into  two  other 
ramps,  leading  up  to  the  bastion  terreplein  on  the  right  and 
left.  Until  the  besiegers  are  about  to  breach  the  bastion  i'accs, 
their  parapets  are  left  intact,  and  the  portions  of  the  cut  along 
which  the  parapets, run  are  filled  tip,  as  in  the  bastion  on  the 
right,  thus  leaving  a  free  communication  throughout  the  inte- 
rior of  the  bastion.  So  soon  as  it  is  thought  neeessarj  to  cut 
off  this  communication,  and  to  get  the  retrenched  portion  in 
a  state  of  defence,  that  portion  of  tjie  parapet  across  the  cuts 
is  demolished,  the  cut  excavated  and  suitably  arranged,  and 
the  parapet  of  the  retrenchment  formed  in  part  of  the  earth 
arising  from  these  changes.  The  parapet  of  the  front  of  the 
retrenchment   is  thrown   back,  leaving  a  corridor  for  sharp- 


choumara's  MiTiion.  163 

shooters  covered  by  A  slight  parapet ;  that  portion  of  this  cor- 
ridor along  the  retired  Rank  being  covered  by  the  earthen 
mask  of  the  orillon.  Choumara  further  proposes,  where  there 
is  a  probability  of  the  scarp  of  the  bastion  face,  which  closes 
the  cut  on  the  exterior,  being  opened,  so  that  a  breach  might 
be  made,  by  firing  through  it,  on  the  flank  of  the  retrench- 
ment, to  run  the  scarp  wall  of  the  retrenchment  at  right  angles 
across  the  cut.  as  shown  on  the  right  faee  of  the  left  bastion, 
and  to  arrange  the  bastionnct,  which  this  modification  would 
give  at  the  shoulder  angle,  for  sharpshooters. 

520. ..To  expose  the  interior  of  the  retrenchment  to  the  fire 
of  the  flanks  of  the  adjacent  bastions,  and  to  the  parapet  of  a 
second  retired  interior  retrenchment,  resting  on  the  two  cur- 
tains adjacent  to  the  bastion,  of  attack,  a  portion  of  the  para- 
pet of  the  bastion  flanks,  near  the  curtain,  is  demolished,  and 
a  slope  is  given  to  the  portion  of  the  terreplein  on  which  it 
re-ted.  The  retired  interior  retrenchment  Choumara  proposes 
to  make  an  earthen-work  in  the  form  of  a  Jiastion'ed  front, 
breaking  the  faces  in  the  most  suitable  manner  to  sweep  the 
rear  of  the  retrenchment  in  its  front. 

•V_'l...The  dispositions  to  convert  the  bastion  into  a  citadel 
are  similar  to  the  preceding,  consisting  of  a  small  front,  the 
faces  of  which  are  nearly  in  the  prolongations  of  the  adjacent 
curtains,  with  oriilons  to  cover  the  corridor  of  tfle  retired 
flank.  This  front  has  a  covered-way  and  glacis  in  advance  of 
it,  the  crest  of  which    masks  the  scar]). 

522. ..Choumara  has  made  an  ample  provision  for  an  easy 
communication  between  all  points  of  the  enceinte  and  the  out- 
works, so  placing  them  as  to  be  well  covered  from  the  besieg* 
erjs  fire  and  well  swept  by  that  of  the  garrison — preferring 
wide  ramps  for  this  purpose.  The  communication  from  the 
enceinte  with  the  main  ditch  is  through  gate-ways  in  the  scarp 
wall  of  the  curtain,  at  its  extremities.  The  ram  pari  at  t; 
points  is  removed  to  the  level  of  the  main  ditch  ;  the  portion 

of   it  between  them,  along  the  Centre  Of  the  CUi;taill,  being  sus- 
tained  at    the   ends  by  revetemenl  walls  run  back  perpendicu- 


lb'-±  <  ii'H  maka's    M  1.1  HOD. 

larly  to  the  scarp  wall  of  the  curtain.  Ramps  lead  from  the 
gorges  of  the  bastions  down  to  these  outlets  into  the  main 
ditch.  From  these  outlets  the  communications  to  the  outworks 
are  around  the  flanks  of  the  tenaille,  and  through  the  enceinte 
ditch,  to  ramps  placed  along  the  enceinte  counterscarp  Leaning 
into  the  demilune,  the  demilune  ditch,  the  enceinte  cov- 
ered-way, and  »its  redoubts  in  the  places  of  arms ;  and  from 
the  demilune  ditch  to  the  redoubt  of  the  demilune  salient 
place  of  arms.  Posterns  on  flie  faces  and  flanks  of  the  bas- 
tions, near  the  shoulder  angles,  lead  to  the  corridors  of  the 
enceinte.  Passages  are  left  at  the  ends  of  the  faces  of  the 
outworks,  leading  from  their  corridors  to  the  interior  of  the 
works.  To  keep  open  the  communication  between  the  bas- 
tions, a  gallery  between  their  gorges  is  made  along  the  curtain 
wall. 

523. ..For  the  security  of  the  casemates,  barricades  can  be 
made  in  their  doors  and  windows,  by  means  of  timber  let  in 
grooves  "made  in  the  walls ;  the  space  between  the  exterior 
and  interior  timber  facing  being  filled  with  sand-bags. 

524... Rkm  auks.  The  memoirs  in  which  Choumara  brought 
his  propositions  before  the  public  naturally  attracted  attention, 
as  much,  perhaps,  from  their  polemical  character  and  piquancy 
of  style  as  their  professional  interest.  They  contain  but  few 
things,  thf  germs  of  which  are  not  to  be  found  in  writers  who 
preceded  him.  His  modifications  respecting  the  parapet^ 
throwing  them  back  from  the  scarps  and  breaking  them  into 
directions  best  suited  for  defence,  are  to  be  met  with  in  CKaa- 
seloxip's  propositions.  His  proposals  for  lengthening  the  bas- 
tion flanks,  and  occupying  the  salient  places  of  arms  by 
redoubts  with  considerable  command,  are  to  t)e  found  in  the 
method  of  cle  la  Ohiche.  To  Virgin  he  seems  to  be  indebted 
for  his  organization  of  interior  retrenchments,  which  are 
to  convert  each  bastion  into  an  independent  work,  equally  pro- 
vided for  defence  against  approaches,  both  from  the  interior 
t  and  exterior  o£  the  enceinte.  Like  disputants,  usually  of  an 
ardent  temperament,  he  over  estimates  the  value  of  many  of 


OBGOTTMASa's   Mi.uitUi.  lti.r> 

his  propositions,  and  loses  sight  of  their  countervailing  defects. 
By  laying  down  as  a  principle  what  may  be  exceptionahly 
good  in  practice,  he  1ms  rather  weakened  hie  own  positions. 
This  is  the  case,  particularly,  with  his.  rule  of  the  independence 

of  the  parapets  on  the  scarps,  which,  if  adopted  in  all  cases, 
might  demand  a  greatly  increased  and  hurtful  command,  and 
cut  up  to  great  disadvantage  the  interior  spaces  of  the  bastions. 
His  introduction  of  the  ehemihs  de  rend  on  the  faces  of  the 
bastion  and  demilune,  add  realty  very  little,  if  at  all,  to  the 
exterior  defence;  whilst  they  contract  the  interior  space  of 
these  works,  break  in  upon  the  unity  of  the  defence,  and 
place  the  troops  in  them  in  a  very  exposed  position  to  the 
means  of  annoyance  possessed  by  the  besieger.  His  expecta- 
tions with  respect  to  the  effect  of  his  fire  in  the  direction  of 
the  capitals,  in  delaying  the  besieger's  approaches  up  to  the 
third  parallel,  were  hardly  warranted  by  tic  experience  gained 
in  artillery  and  small  arms,  even  at  the  time  the  last  edition 
of  his  memoirs  appeared.  It  is  hardly  to  be  questioned,  now 
that  these  weapons  have  been  so  greatly  improved,  both  in 
range  and  accuracy  of  fire,  that,  considering  the  increased  de- 
velopment of  the  besieger's  parallels,  which  gives  him  a  choice 
of  positions  for  his  batteries  on  so  extended  a  line,  the  concen- 
trated fire  he  could  bring  to  bear  on  the  batteries  in  question 
would  not  only  soon  ruin  their  casemates,  but  would  greatly 
damage  the  adjacent  faces,  and  also  the  thinks  of  the  bastions, 
although  covered  from  enfilading  views,  either  by  the  direc- 
tion of  the  parapets  of  the  faces  or  the  high  traverses  raised 
with  the  same  Object  These  advantages  in  the  position  of  the 
besieger,  it  is  thought,  would  prevent  any  delay  in  pushing 
forward  his  approaches  up  to  the  third  parallel.  After  this, 
the  approaches  would  probably  be  retarded  beyond  the  usual 
time  allowed  in  the  attack od  Cormoritairijme's  front,  owine 
chiefly  to  the  redoubts  in  the  bastion  ami  demilune  Balient 
places  of  arma  ;md  the  arrangement   of  the    fa  r    in   the 

ditch. 

Supposing    an  enceinte    organized    according   to  his 


166  coehorn's  method. 

method,  and  containing  interior  retrenchments  to  oppose  the 
besieger's  approaches,  both  from  without  and  within  the  en- 
ceinte, (Jhoumara  estimates  at  least  six  separate  epochs  of 
breaching  batteries,  as  follows:  1st,  against  the  redoubt  of  the 
demilune  salient  place  of  arms;  2d,  against  the  demilune' and 
the  redoubt  of  the'bastion  salient  places  of  arms ;  3d,  against 
the  bastions;  4th,  against  the  bastion  retrenchment;  5th, 
against  the  retired  retrenchment ;  6th,  and  finally,  against  the 
bastions  converted  into  citadels  by  the  fronts  with  which  their 
gorges  are  closed.  According  to*  the  estimate  of  time  made 
by  Choumara,  it  would  re<jutre  112  days  from  the  opening  of 
the  trenches  to  the  final  assault  and  reduction  of  the  last  de- 
fences. 


COEHOBJTS   METHOD, 


526...Coehorn,  a  Dutch  engineer  of  great  eminence,  was  the 
contemporary  and  rival  of  Yauban,  both  in  actual  warfare  and 
in  the  engineer's  art.  Like  Yauban,  he  is  the  author  of  sew 
eral  methods,  in  which  he  has  shown  the  same  preeminent 
skill  as  Yauban,  in  the  adaptation  of  his  art  to  local  features, 
and,  perhaps,  more  originality  in  his  combinations;  for  Yau- 
ban rather  made  use  of,  and  improved  upon,  the  defensive 
branch  of  his  art,  as  he  found  it,  than  originated:  whereas, 
many  of  Coehorn's  devices  are  his  own. 

527...Coehorn's  fronts  are  arranged  with  a  view  to  aquatic 
sites,  like  those  of  Holland,  where  water  is  found  by  excavat- 
ing to  the  depth  of  a  few  feet  below  the  natural  surface,  by 
means  of  which,  wet  ditches  can  be  combined  with  those 
which  are  dry,  so  as  to  procure  not  only  security  against  a 


coehorn's  method.  167 

surprise,  but,  as  will  be  seen  further  on,  to  afford  facilities  for 
an  active  defence  against  the  enemy  when  in  possession  of  the 
dry  ditches. 

528. ..Plan.     Coehorn  has  adopted  the  mode  of  laying  out 
the  lines  of  his  front,  used   by  some  of  the  earlier  engineers; 
fixing,  in  the  first  place,  the  inferior  sides  of  tlfb  space  to  be' 
enclosed,  taking  these  lines  as  the  magistrals  or  exterior  lines 
of  the  curtains  in  the  bdstfoned  system. 

52i>. ..Assuming  A  B,  PI.  15,  as  the  position  of  the  interior 
side,  Coehorn  makes  its  half  length,  A  B,  75  toises,  French 
measure.  From  A,  the  same  distance,  75  toises,  being  set  off 
to  C,  on  the  capital,  or  bisecting  line  of  the  angle  of  the  poly- 
gon, gives  the  salient  of '  the  exterior  side;  this  side  in  the 
hexagon  being  224  toises.  Bisecting  A  B,  the  half,  B  I),  is 
taken  for  half  the  curtain. 

The  lines  of  defence  are  drawn  from  the  extremities  of  the 
curtain,  thus  determined,  to  the  opposite  salients  of  the  ex- 
terior side.  From  the  salients  of  the  exterior  .-id.-,  as  centres, 
with  the  lines  of  defence  as  radii,  arcs,  1)  G,  being  described, 
give  the  faces,  C  G,  of  the  bastions  measured  along  the  lines 
of  defence. 

The  portions  of  the  faces  thus  determined  are  not  revetted 
toward  the  ditch;  the  exterior  slopes  of  their  parapets  descend- 
ing below  the  water  level  to  the  bottom  of  the  ditch,  as  shown 
on  the  cross  section  (i'  If. 

530.. .At  the  shoulder  angle  of  the  bastion,  Coehorn  has 
placed  a  stone  tower,  of  which  Q  I  I.  K  //is  the  plan. 

An  interior  elevation  of  this  tower  is  shown   on   the  section 

Q  R.     This  tower  ii  arranged  on  top  with   a   parapet  for  an 

open  defence.     It  is  arranged  with  bomb-proof  arches,  and  is 

coated  on  the  interior"  side,  Q  II.  to  Bweep  the  drv  ditch 

between  the  bastion  and  the  Cavalier  within  it. 

'I'..  se1  mit  the  tower,  0  II  is  drawn  perpendicular  to  0  <\ 
and  18  toisee  in  length;  a  distance,  0  I.  of  S^  toit  tdken 

on  the  prolongation  of  ('  C  f  II  I\  is  drawn  parallel  to  0  I. 
audi  toises  in   length;    KL   is  found   by  joining  A' with    the 


168 


COEUORN  S    METHOD. 


c 


opposite  salient,  making  K L  equal  to  14  toises  taken  along 
this  line^  the  points,  1  and  Z,  thus  determined,  are  joined  by 
an  arc  of  60°. 

The  curved  projecting  portion  of  the  tower  forms  an  orillon, 
which  covers  the  concave  flank  P  D,  which  is  also  an  arc  of 
60°.  •  . 

531. ..The  faces  and  flanks  of  the  cavalier  have  a  revetted 
scarp,  as  well  as  the  portion  I)  S  of  the  curtain;  which  is 
thrown  back  on  the  prolongation  of  the  line  of  defence,  and 
closes  the  gorge  of  the  bastion.  The  magistral  of  the  face  of 
the  cavalier  is  parallel  to  C  G',  and  -J^.V  toises  from  it.  The 
magistral,  0  S,  of  the  flank  is  concentric  with  the  one,  P  D, 
of  the  bastion,  a  ditch  16  toises  wid'e  being  left  between  the 
two  flanks. 

532. ..The  interior  of  bastion  face  C  Gf  which  forms  the  coun- 
terscarp of  the  cavalier,  is  arranged  with  a  loop-holed  gallery 
for  sweeping  the  cavalier  ditch. 

533. ..The  space  between  the  orillons  and  curtain  is  occupied 
by  a  tenaille,  of  which  I  U  T  Vis  the  exterior  line  at  the 
water  level.  The  point  T  is  on  the  line  of  defence,  and  at  140 
toises  from  the  salient ;  the  portion  T  IT  is  perpendicular  to 
this  line  of  defence,  and  the  portions  /  £7  and  T  V  are  on  the 
lines  of  defence. 

534.. .The  enceinte  ditch  is  24  toises  wide  at  the  water  level. 
An  earthen  counterguard,  D  C\  for  musketry  defence  is  placed 
in  front  of  the  bastion. 

535. ..The  6alient,  Z,  of  the  demilune  is  at  93  toises  from  the 
point  IF,  where  the  enceinte  counterscarp  cuts  the  capital  of 
the  front ;  its  demigorge,  W  £',  is  534,  toises.  The  demilune 
ditch  is  IS  toises  wide,  and  that  of  the  counterguard  is  14 
toises. 

536. ..The  demilune  contains  a  small  redoubt,  the  faces  of 
which  are  revetted,  and  parallel  to  those  of  the  deinilune.  The 
ditch  of  the  redoubt  is  dry,  and  16  toises  wide.  A  curvilinear 
space  is  formed  at  the  gorge  of  the  redoubt,  to  afford  a  covered 
harbor  for  boats  used  for  communication.     A  small  capon- 


t  coehokn's  method.  •  169     • 

mere,  in  the  form  of  a  lunette,  is  placed  at  the  gorge  of  the  re- 
doubt to  seenre  the  retreat  of  the  troops  from  it  to  the  boats. 
The  walls  of  this  caponniere  are  pierced  with  two  tiers  of  loop- 
holes ;  the  work  being  divided  into  two  stories,  the  lower  be- 
ing covered  with  heavy  beams  and  earth  to  resist  shells,  the 
upper  being  uncovered. 

537.. .A  similarly  covered  caponniere,  of  a  rectangular  shape, 
for  one  tier  of  fire,  is  placed  across  the  ditch  of  the  redoubt, 
near  its  extremity.  A  small  -wet  ditch  is  placed  in  front  of 
this  work,  and  is  flanked  by  a  counterscarp  gallery  under  the 
portion  of  the  demilune  face  opposite  to  it. 

53S...A  like  construction,  of  a  pentagonal  form,  is  placed 
within  the  salient  angle  of  the  demilune,  the  faces  of  which, 
toward  the  interior  of  this  work,  arc  loop-holed  to  sweep  the 
ditch  of  the  redoubt  and  the  interior  of  the  demilune. 

539.. .The  covered-ways  of  the  counterguard  and  demilune 
are  13  toises  wide  ;  a  reentering  place  of  arms  is  formed  at  the 
junction  of  the  two,  the  faces  of  which  are  30  toises. 

54<>...A  redoubt  of  a  quadrangular  shape,  the  faces  *>f  which 
are  respectively  12  and  15  toises,  and  which  is  a  simple  loop- 
holed  wall,  closes,  in  connection  with  two  traverses,  the  gorge 
of  the  reentering  place  of  arms. 

541. ..A  gallery,  covered  with  heavy  timber  and  earth,  is 
placed  f>  toises  in  advance  of  the  reentering  place  of  arms,  to 
furnish  a  fire  of  musketry  to  sweep  the  glacis  in  front. 

One  of  the  most  prominent  features  in  Coehorn  s  method  is 
the  combination  of  wet  and  dry  ditches,  with  a  view  to  secur- 
ity from  surprise,  and  for  protracting  the  defence  and  disput- 
ing the  ]m  of  every  point  foot  by  foot.  For  these  purr 
-  the  wet  ditches  are  made  M-ry  wide  and  contain  water, 
at  Least  six  feet  in  depth,  thus  forcing  the  enemy  to  the  con- 
struction of  long  dikes  to  effect  their  passage  ;  whilst  the  bot- 
,toin  of  the  dry  ditches  uoe  kept  slightly  above  the  general 
water  level,  so  a>  to  compel  th«'  enemy  to  bring  the  earth,  as 
well  as  the  other  materials  r<  quisite  for  their  passage,  from 
other  points.     In  addition  to  these  purely  passive  mea.is,  the 


170  coehorn's  method. 

dry  ditches  are  organized  for  an  active  defence  by  sorties,  and 
are  well  swept  by  direct  and  reverse  fires  from  casemates, 
counterscarp  galleries  and  oaponnieres.  The  portion  of  the 
dry  ditch  between  the  faces  of  the  cavalier  and  bastion  is  swept 
by  artillery  in  the  casemates  under  the  orillon,  and  by  two 
pieces  behind  a  wall  pierced  with  embrasures,  which  closes  the 
space  between  the  shoulder  angle,  0,  of  the  cavalier,  and  the 
extremity,  JI K,  of  the  orillon.  In  like  manner,  the  ditch  be- 
tween the  flanks  is  swept  from  casemates  under  the  portion  S 
D  of  the  curtain.  A  reverse  fire  of  musketry  sweeps  .the  ditch 
along  the  face,  from  counterscarp  galleries  under  the  bastion 
faces,  and  from  a  gallery  along  the  capital,  which  serves  as  a 
communication  between  these  galleries  and  the  interior. 

To  cut  off  the  communication  between  the  ditch  of  the  face 
and  flank,  a  wet  ditch  is  made  in  front  of  the  orillon  and  the 
connecting  wall.  This  ditch  is  flanked  by  the  counterscarp 
gallery.  Two  drawbridges  over  this  ditch  form  a  means  for 
sorties  on  the  enemy  whilst  effecting  the  passage  of  the  ditch 
of  the  face.  A  drawbridge  for  a  like  purpose  is  thrown  over 
the  wet  ditch,  in  front  of  the  caponniere  in  the  ditch  of  the 
demilune  redoubt.  Besides  these  provisions  for  carrying  on 
what  the  French  well  express  by  une  guerre  de  chicane,  Coe- 
liorn  makes  a  profuse  use  of  palisadings  in  all  parts  of  his 
front  where  an  obstinate  stand  is  to  be  made,  besides  employ- 
ing countermines  to  destroy  such  parts  as,  being  in  the  enemy's 
possession,  would  be  prejudicial  to  the  defence. 

542.. .The  question  may  very  naturally  be  here  asked,  to 
what  extent  such  means  of  defence  may  be  depended  upon  ? 
The  answer  is,  only  so  far  as  they  can  be  kept  in  a  good  con- 
dition for  the  moment  when  they  can  be  brought  into  play. 
With  the  present  improved  practice  of  artillery  there  is  little 
doubt  but  that  all  of  these  means  for  the  ditch  defences,  as 
rovided  by  Coehorn,  except  the  counterscarp  galleries,  would 
e  destroyed  by  the  ricochet  fire  of  the  enemy's  enfilading 
batteries  at  an  early  period  of  the  siege,  the  masonry  of  the 
loop-holed   redoubts   and    caponnieres    being   altogether  too 


coehorn's  method.  171 

slight  to  withstand  the  effects  of  this  fire.  Could  these  means 
be  kept  in  a  good  condition,  we  have  the  warrant  of  numerous 
sieges  in  favor  of  their  efficacy  in  the  Jiands  of  an  intelligent 
and  resolute  garrison. 

543... Profiles.  In  the  plan  and  profiles  the  horizontal 
plane  of  site  is  assumed  at  24  feet  above  the  plane  of  compari- 
son. From  an  examination  of  the  references  on  the  figures  of 
the  plate,  the  relief  and  relative  command  of  all  the  works  are 
readily  deduced.  It  will  be  seen,  on  examining  the  plan,  that 
a  portion  of  the  bastion  face,  adjoining  the  salient,  is  raised  3 
feet  higher  than  the  portion  toward  the  orillon,  thus  forming  a 
bonnctte,  which  not  onlv  gives  a  greater  command  to  this  por- 
tion, but  masks  more  effectually  the  ditch  and  fhasonry  of  the 
cavalier.  A  like  arrangement  is  seen  in  the  demilune  face, 
both  at  the  salient  and  toward  the  gorge,  and  with  a  like  view 
to  mask  the  caponniere  and  the  loop-holed  redoubt  in  the 
salient  of  the  demilune. 

544... Remarks.  It  will  be  seen,  on  reference  to  the  plan 
and  sections,  that  Coehorn  has  given  but  a  slight  command  to 
all  his  works — his  object  in  this  being  economy,  and  to  depend 
rather  upon  the  near  titan  the  distant  defence,  his  dispositions 
having  been  made  almost  exclusively  for  the  former.  The 
command  of  the  crest  of  the  covered- way  is  only  44,  feet  over 
the  natural  site,  the  terreplein  of  this  work,  which  is  74;  feet  be- 
low the  crest,  being  thus  placed  a  little  above  the  water  level, 
with  a  view  to  compel  the  besiegers  to  bring  the  earth  and 
materiel  from  a  distance  to  form  a  cover  for  his  approaches  in 
the  covered-way. 

545. ..The  only  dispositions  for  the  distant  defence  by  artillery 
are  in  the  cavalier  and  demilune  redoubt,  except  in  the  dry 
ditches,  where  gun.-  and  mortars  might  be  placed  to  fire  over 
the  low  parapets  of  the  exterior  works. 

546...Beaides  the  exposure  to  ricoehel  caused  by  this  slight 
Command,  the  directions  given  to  all  the  faces  of  the  works  arc 
rery  favorable  to  the  enemy's  enfilading  batteries. 

547. ..The   dimensions  of  the    parapet  of  the  counterguurd. 


172  TENAILLKD    SYRTKM. 

which  serves  as  a  mask  for  the  triple  flank  fire  of  the  cavalier, 
bastion  and  tenaille,  and  those  of  the  parapets  of  the  bastion 
and  demilune,  which  se/ve  as  face  covers" for  the  cavalier  and 
demilune  redoubt,  are  insufficient  for  these  purposes,  as  they 
could  readily  be  opened  "by  shells  fired  horizontally  into  them, 
or  by  small  mines,  and  expose  the  scarp  of  the  interior  works 
to  the  enemy's  breach  batteries  on  the  glacis.  The  scarp 
walls,  moreover,  of  the  works  in  question,  are  not  of  sufficient 
height  to  secure  them  from  an  open  assault.  The  only  feature, 
then,  of  the  ingenious  combinations  of  this  celebrated  engineer, 
which  would  find  an  application  in  the  present  state  of  the  art, 
is  the  combination  of  wet  and  dry  ditches  for  sites  similar  to 
those  for  which  his  dispositions  were  designed. 


TENAILLED    SYSTEM. 


548. ..Several  engineers,  of  professional  eminence,  have  pro- 
posed tenailled  enceintes,  as  offering  defensive  properties  su- 
perior to  bastioned  enceintes.  This  system  has  found  but  few 
advocates ;  and,  except  in  particular  localities,  where  the  na- 
tural features  of  the  site  demanded  it,  and  for  small  works,  it 
has  met  with  no  practical  applications. 

549. ..Requiring  that  the  salient  angles  shall  not  be  less  than 
60°,  and  the  reentering  angles  between  90°  and  100°,  the 
tenailled  system  is  only  adapted  to  regular  polygons/of  a  suffi- 
cient number  of  sides  to  admit  of  these  conditions  being  satis- 
fied. If  the  exterior  sides  are  kept  within  the  limits  usually 
admitted  by  engineers  for  bastioned  enceintes,  the  faces  of  the 
tenailles  become  very  long  and  the  reenterings  very  deep ; 
thus  presenting  two  serious  defects :  long  lines  which  are  very 


CARNOT  S   TKNAILLED   1METH0D.  173 

f 

much  exposed  to  enfilade,  and  a  great  diminution  of  the  inte- 
rior space  as  compared  with  the  bastioned  enceinte.  The 
ditches  when  dry  can  only  be  swept  by  casemated  defences»in 
the  reentering  angles;  and  even  then  but  partially,  unless  the 
casemate  embrasures  are  placed  very  mar  the  level  of  the  bot- 
tom of  the  ditch,  in  which  case  the  enceinte  would  be  exposed 
to  a  surprise  through  the  embrasures  ;  and,  in  the  contrary 
case,  liable  to  a  like  attempt  from  the  dead  space  at  the  re- 
enterings  below  the  embrasures.  In  wet  ditches  this  exposure 
to  surprise  would  be  much  less  if  the  ditches  could  not  be 
forded.  In  either  case  the  defect  arising  from  embrasure  case- 
mates placed  in  the  reentering  angle,  would  be  a  serious  ob- 
jection to  using  the  guns  of  each  side  simultaneously.  When 
the  salient  angles  of  the  tenailles  are  acute,  the  effect  of  the 
enfilading  fire  would  not  be  felt  alone  on  the  face  enfiladed, 
but  upon  the  adjacent  face  in  front,  and  shot  passing  over 
would  damage  the  adjacent  tenailles. 

The  foregoing  are  the  chief  objections  to  this  system.  It 
presents  no  advantage  but  the  very  illusory  one,  considering 
the  consequences  arising  from  it,  of  long  faces  presenting  a 
mutual  flanking  and  cross  fire  ojf  considerable  extent. 


CARNOT' S    TENAILLED   METHOD. 


550. ..The  great  reputation  acquired  by  Carnot  during  the 
French  revolution,  in  which  lie  played  so  eonspicuotiB  a  part 
MB  a  soldier,  statesman  and  executive  officer,  connected  with 
his  professional  education  as  an   engineer  officer,  gav$  for  a 

time  a  certain   j>r<*li<je   to   his    views    on    fortification,  which 


174  CARNOt's   TENAILLED   JIETHOD. 

I 
caused  them  to  be  adopted  in  Germany,  where  they  have  been 
applied  in  some  of  the  works  constructed  since  1815. 

£51. ..Struck  with  the  exposed  state  of  the  artillery,  on  ram- 
parts without  bomb-proof  shelters,  to  ricochet  fires,  and  the 
feeble  resistance  offered  by  garrisons  in  some  of  the*  sieges  of 
his  day,  particularly  in  an  active  defence  by  sorties,  Carnot 
seems  to  have  considered  the  weakness  attributed  to  existing 
fortifications  to  the  want  of  such  shelters,  and  also  of  such 
means  of  communication  with  the  exterior  which  would  ena- 
ble the  garrison  to  sally  out  in  force  and  assail  the  trenches 
of  the  besiegers. 

552.. .The  systems  of  defence  which  he  has  proposed  are  de- 
vised to  remedy  these  two  prominent  defects,  and  consist  in 
providing  a  number  of  casemates,  on  suitable  points  of  the 
defences,  from  which  a  constant  shower  of  small  projectiles 
and  hollow  shot  can  be  brought  upon  the  besieger's  works ; 
and,  instead  of  the  revetted  counterscarp,  which  constitutes 
one  of  the  main  securities  against  a  surprise — but  as  ordinarily 
arranged  is  an  obstacle  in  the  way  of  throwing  rapidly  for- 
ward a  considerable  body  of  troops  from  the  interior  to  oper- 
ate on  the  exterior — he  proposes  to  form  an  earthen  one  with 
so  slight  a  slope  that  troops  can  ascend  it  with  ease  to  make 
sorties ;  the  ordinary  covered-way  and  glacis  being  also  done 
away  with  to  facilitate  these  operations. 

553. ..Carnot,  in  his  published  works,  has  given  his  views 
upon  the  ameliorations  of  which  the  fortifications  of  his  time 
were  susceptible,  besides  some  new  combinations  for  a  bas- 
tioned  system  and  two  tenailled  systems  for  aquatic  and  irreg- 
ular sites,  in  which  the  defects  of  this  latter  system  are  less 
objectionable,  and  to  which  they  can  J3e  more  easily  applied. 

554.. .Plan.  This  consists  of  a  continuous  enceinte,  PL  16, 
Pig.  2,  formed  of  tenailles,  the  reentering  angles  of  which  are 
90°,  and  the  salient  angles  not  less  than  60°.  The  interior  of 
the  place  is  enclosed  by  a  wall,  A,  of  sufficient  height  to  be 
secure  from  escalade  ;  the  plan  of  it  is  a  tenailled  line,  with 
reentering  angles  of  90°  and  salients  of  60° ;  it  is  arranged  with 


carnot's  tenailled  method.  175 

two  tier*  of  loop-holes  for  musketry,  which  arc  within  arched 
recesses  in  the  wall,  of  sufficient  depth  to  screen  the  men  serv- 
ing them  from  vertical  fire.  Casemated  batteries,  Q,  for  artil- 
lery, are  placed  at  the  reenterings,  to  flank  the  ditch  between 
the  wall  and  tlie  earthen  rampart  of  the  enceinte.  This  wall 
serves  the  same. end  as  the  one  in  Montalembert's  method. 
The  salients,  A  A,  are  about  250  yards  apart. 

555. ..The  rampart  and  parapet  of  the  body  of  the  place,  O, 
are  detached  from,  the  scar])  wall  in  front,  a  narrow  corridor 
being  left  between  the  foot  of  the  exterior  slope  and  the  bach 
of  the  wall.  The  wall  is  arranged  like  the  interior  one,  with 
one  tier  only  of  loop-holes  for  musketry  fire.  At  its  reentering 
it  is  broken  forward  and  is  pierced  with  embrasures,  to  form  a 
position,  TF,  for  cannon  to  flank  the  ditch  between  it  and  the 
tenaille. 

550. ..The  tenaille,  G,  masks  the  greater  portion  of  the  scarp 
of  the  body  of  the  place,  its  wings  being  about  120  yards  in 
length  ;  it  is  closed  by  a  detached  wall  with  loop-holes. 

557. ..From  the  reentering  of  the  tenaille  a  double  caponniere 
of  earth  leads  by  a  ramp  to  an  earthen  redoubt,  A*,  placed  at 
the  reentering  formed  by  the  counterscarps.  This  redoubt  is 
intended  to  hold  troops  in  readiness  for  sorties,  and  is  without 
a  ditch,  so  that  they  can  move  out  over  its  parapet' 

558. ..Earthen  conntergnards,  the  salients  of  which,  B  B,  are 
about  390  yards  apart,  mask  the  walls  of  the  bodv  of  the  place 
and  the  tenaille;  sufficient  space  only  being  left  between  their 
extremities,  I1]  F,  and  the  caponniere  for  the  circulation 
through  the  ditches.  This  work,  like  the  tenaille,  has  a  narrow 
terreplein,  and  is  intended  only  for  a  defence  of  musketry,  ex- 
cept at  the  salient  portions,  which,  like  the  salients  of  the  en- 
ceinte, are.  arranged  t'<>r  artillery  to  fire  in  the  direction  of 
their  capitals  from  behind  blindages  or  calcinated  traverses. 

The  foot  of  the  parapet,  M  .1/,  of  the  reddnbt  is  placed  40 
yards  within  the  line  joining  II  II. 

55H...PK"!  ii.k.  The  positions  of  the  different  lines  on  the 
plan  are  readily  ascertained  from  the.  section  on  ■/  1\\  Fig.  9, 


176  POLYGONAL    SYSTEM. 

as  the  lilies  are  all  parallel.  The  relief  and  the  relative  com- 
mand of  the  different  parts  are  also  given  on  the  same  section. 
560.. .Remarks.  The  expectations  of  Carnot  with  respect  to 
the  efficacy  of  the  proposed  shower  of  small  projectiles  upon 
the  trenches  of  the  besiegers,  from  the  casemates  for  mortars 
and  howitzers,  have  been  shown  from  experiments  as  not  likely 
to  be  realized.  From  similar  experiments,  the  detached  scarp 
walls  proposed  by  him  would  soon  be  overthrown  by  a  heavy 
curvated  iire,  which  might  be  brought  to  bear  upon  them  over 
their  earthen  masks.  The  ditches  and  terrepleins  of  all  the 
parts  of  his  tenailled  method  are  peculiarly  exposed  to  rico- 
chet fire,  whilst  the  long  wings  of  the  tenaille  and  the  double 
caponniere  mask,  to  a  great  degree,  the  fire  of  the  enceinte 
along  the  ditches.  The  provision  made  for  sorties  from  there- 
doubt  at  the  reentering  of  the  earthen  inclined  counterscarps 
is  exceeding^  feeble,  and  it  is  not  easy  to  see  what  would 
prevent  an  active  enemy,  on  the  repulse  of  a  sortie,  from  fol- 
lowing the  retreating  troops  into  the  works  themselves,  or, 
having  driven  them  into  the  ditches,  from  regaining  their 
trenches  with  comparatively  little  loss. 


POLYGONAL   SYSTEM. 


561. ..The  polygonal  system  has  been  proposed  by  several 
engineers  of  distinction,  but  its  most  ardent  advocate  has  been 
the  celebrated  Montalembert,  whose  views  have  been,  more  or 
less,  carried  out  in  many  of  the  more  recent  constructions  of 
the  engineers  of  Germany. 

Consisting  of  either  a  simple  polygonal  enceinte  without  re- 
enterings,  the  sides  of  which  are  flanked  by  casemated  capon- 


POLYGONAL    SYSTEM.  177 

niercs,  placed  at  the  middle  point  of  the  fronts;  or  of  fronts 
either  slightly  tonailled,  or  of  a  bastioned  form,  with  short 
casemated  flanks  to  flank  the  faces  of  the  central  caponniercs. 
this  system  affords  more  interior  space,  and,  from  the  mode 
adopted  for  flanking  the  enceinte,  will  admit  of  much  larger 
fronts  than  either  the  bastioned  or  the  tonailled  systems.  The 
salient  angles,  moreover,  will  be  more  open  in  this  than  in  the 
other  two  systems.  From  these  peculiarities  of  this  system, 
the  positions  suitable  for  the  erection  of  batteries  to  enfilade 
the  faces  of  the  enceinte  are  less  advantageous,  from  their 
being  thrown  in  nearer  to  the  adjacent  fronts,  than  in  either 
of  the  other  systems;  whilst  a  greater  development  of  trenches 
will  also  be  requisite  to  envelop  the  fronts  of  attack.  These 
obvious  advantages,  however,  are  more  than  counterbalanced 
by  the  want  of  the  concentrated  cross  fires  which  are  afforded, 
in  both  the  bastioned  and  tenailled  systems,  in  advance  of  the 
salients  of  the  enceinte,  and  upon  the  ground  generally  in  ad- 
vance of  the  fronts.  Each  front  of  the  polygonal  system 
offers,  moreover,  a  long  and  vulnerable  line  to  enfilading  and 
slant  fire,  which  will  also,  to  some  extent,  take  effect  on  the 
reverse  of  the  adjacefit  fronts.  Bnt  the  chief  objection  to  this 
system  lies  in  the  mode  adopted  for  flanking  the  enceinte. 
The  casemated  capnnniores fof  this  purpose  being  exterior  to 
the  enceinte,  it  will  be  exposed  t<>  escalade  as  soon  as  the  fire 
of  the  caponniercs  is  silenced,  which,  considering  the  structure 
of  the  caponniere,  and  the  exposure  of  its  embrasures  to  the 
enfilading  batteries,  will,  in  all  probability,  take  place  at  an 
early  period  after  this  fire  is  opened. 


178  MONTALKMBEBTfi    POLYGONAL    METHOD. 


MO.XTALKMUEKT'S    POLYGONAL    METHOD. 


r.«'.^ — \ nit .nir  the  writers  on  permanent  fortification  wh< 
works  have  had  an  importaut  beariug  on  the  progress  of  the 
art,  Montaleinbert  holds  a  conspicuous  place,  although  not 
educated  as  an  engineer.  Struck  by  the  evident  defects  of  the 
methods  of  his  predecessors,  particularly  the  want  of  c 
mates,  both  for  defensive  dispositions  for  artillery  and  mus* 
ketry  and  the  shelter  of  tin-  garrison  and  munitions,  Montalem- 
oerl  devoted  his  time,  talents  and  fortune,  to  bringing  about  a 
change  in  the  direction  in  which  it  seemed  to  him  called  tor. 
His  efforts,  however^  led  to  no  modifications  of  consequence 
during  his  life  (which  was  principally  spent  in  angry  contro- 
versies with  his  opponents),  except  the  extension  of  casemated 
defence.-  Cor  sea-coast  works;  and  it  is  only  within  a  compar&t 
lively  H-ccnt  period,  since  the  termination  of  the  great  wars  in 
Europe,  in  the  present  century,  thai  a  new  school  of  engineers 
has  grown  Jtp  in  <  ierinany,  based  upon  the  views  put  forth 
mainly  by  Montalemhert ;  and  that  these  views  have  met  with 
iavor  in  other  parts,  although  still  opposed  by  many  aide  en- 
gineers, in  all  countries,  who  contesl  their  soundness. 

563.. .The  principal  propositions  of  Montalemhert  consist  in 
the  entire  rejection  of  the  bastioned  system  as,  according  bo 
his  views,  unsuitable  to  a  good  defensive  disposition;  and  in 
its  steiad  he  proposed  to  ule  either  the  tenailled  system  or  the 
polygonat  system  ;  in  basing  the  Btrength  of  these  last  systems 
upon  an  overwhelming  force  of  artillery  fire  in  defensive  case- 
mates, and  in  organizing  Btrong  permanent  works  within  and 
independent  of  the  body  of  the  place,'  which  are  to  serve  as  a 
secure  retreat  for  the  garrison  when  forced  to  give  up  'its 
defence. 

564.;.  M"  t   of  the   objections  urged  against  the   bastioned 


montalembert's  polygonal  method.  1  7!» 

SysteM  and  its  outworks  haVing  al ready  hecn  adverted  to  in 
the  analysis  of  the  front,  it  will  lie  unnecessary  to recap! tulate 
them  here;  arid  as  the  teuaflled  Bystem,  Composed  of  faces  of 
equal  lengths,  with  reentering  angles  of  t0°  and  salient  ang 
6f  60*,  and  termeil  by  Montalemhert  pt  ,-j><  wdifn il.tr  forfijica- 
timi,  from  the  position  of  the  faces  at  the  reentering*,  lias 
many  obvious  and  mora  serious  defects  than  either  of  the 
other  two;  it  is  proposed  to  give  here  a  description  of  the 
polygonal  system  alone,  and  that  in  its  most  simple  form;  the 
one  in  which  Ifontalembert  presented  it  for  the  fortifications 
at  Cherbourg,  one  of  the  most  important  naval  stations  in 
France. 

56.">...Montaletnhert  first  gave  the  name  polygonal  system  to 
a  trace  of  the, enceinte  in  which  all  of  the  angles  are  either 
salient,  or  where  the  reenterings  are  very  alight  The  distinc- 
tive of  his  method  are  shown  in  the  works  which  he 
projected  for  the  defence  of  the  harbor  of  Cherbourg. 

In  tine  tract'  proposed  for  this  places  .\'  }'.  Fig. 
1.  PL  16,  ifl  the  exterior  side,  or  direction  of  the  scarp.  The 
body  «»f  the  place  consists  of  the  scarp  wall,  I),  Fig.  1,  and 

on   on  /'  <j,  arranged  with  oasesnates  for  artillery  and 

Bketry;  of  a  corridor,  (7,  between  these  casemates  and  the* 

en  rampart  and  parapet,  //.      In   rear  of  the  rampart  ii  a 

high  wall,  A.  arranged  with  loop-holes,  within  which  the  gar* 

rison  retires  when  driven  from  the  defence  of  the  rampart. 

:...<  lasemai ed  caponnieres,  .V.  which  are  secure  from  a 
coupdi  mam,  are  placed  along  the  rampart,  and  so  arrai 
that  a  fire  can   be   thrown   from   them    over   the    parapet,  and 

along  the  terreplein.    The  conidor,  < .  is  also  -wept   by  I 

mated  caponniere,  6-',  for  musketry,  and  the  tVont    of  the 
wall,  A .  by  a  lil  -it. 

:pal  caponniere  for  hanJcing  the  main  ditch 

i-  in  the  fom   of  a  lunette,  and    i  .:    the    middle   of   the 

■ 
the  flanks,  //.  and  t  A .  ol   fab 

!  with   two    1  artillery    and    musketry    fire, 


lv"  Mi'MAI.I  M!:J  IM*s    POLYGONAL    Mi:nit>l>. 

each  flunk  carrying  ten  pins,  and  each  face  twelve  guvs.  A 
wet  ditch,  A  separates  the  faces  and  flanks;  a  loop-holed  wall 
encloses  the  portion  between  the  Hanks,  from  which  the  oppoi 
site  portion  between  the  faces  is  swept  by  musketry. 

569.. .The  caponniere  is  covered  in  front  by  a  face  oov.er,  A', 
od  earth  in  the  shape  of  a  redan.  The  scarp  of  the  enceinte  is 
etiveped  in  Like  manner,  by  the  continuous  face  cover,  0,  of 
earth)  in  the  reentering  afaglea  of  which,  caseniatcd  1  «at t . 
ol  two  stories,  for  artillery  and  musketry,  are  placed  to  flank 
the  ditches,  and  sweep  the  positions  for  counter-batteries 
around  the  salients  of  the  covered-way.  These  batteries  are 
masked  in  front  by  the  earthen  works,  <S  and  Q.  The  whole 
is  covered  by  the  covered-way,  arranged  in  the  usual  manner. 

The  better  to  flank  the  main  caponniere,  the  portion  of  the 
caseniatcd  gallery  joining  it  is  arranged  with  two  tiers  of  artil- 
lery fire,  the  remaining  portion  having  but  one  tier  of  gabs. 

570...Pbobtlbb,  The  sections  along  J3  Q,  R  S,  and  T  U, 
show  the  relative  eoiiiniand  of  the  different  works,  and  the 
width  of  the  ditches  and  earthen  ramparts. 

The  coimnunieatioiis  between  the  different  works  are  by 
bridges  across  the  wet  ditches.    . 

•  571. ..It  is  now  admitted  on  all  bands  that,  although  Mon- 
talembert  has  rendered  important  services  to  the  progres 
fortification,  particularly  as  regards  the  more  extensive  em- 
ployment of  caseniatcd  defences,  still,  many  of  his  projects 
were  visionary.  How  far  the  recent  works  constructed  in  Eu- 
rope, which  are  based  on  his  views,  will  answer  their  ends, 
remains  to  be  seen  by  the  test  of  actual  siege  operations  against 
them. 

The  partisans  for  and  against  these  views  are  equally  confi- 
dent in  their  arguments ;  but  with  the  rapid  improvement  in 
artillery  which  has  taken  place  within  the  last  few  years,  and 
the  heavier  calibre  which  will  doubtless  be  hereafter  used  ill 
siege  operation,  it  is  very  doubtful  whether,  from  what  expe- 
rience has  already  shown  as  to  the  effects  of  artillery  on  case 
mate  defences,  they  will  be  found  to  withstand  these  powerful 


L'IMM     i, I  l.'MAN     FORTIFICATIONS.  181 

means,  in  which  case  the  systems  based  upon  Montalembert'l 
view  must  fall  to  the  ground. 


RECENT    GERMAN    FORTIFICATIONS. 


5T2..Jj3  the  large  additions  made  to  the  fortifications  of  the 
German  States  since  the  general  peace  in  Europe  in  1815,  the 
man  engineers  have,  for  the  most  part.  <>f  these  new  struc- 
tures, embraced  the  ideas  put  forth  in  the  works  of  Montalem- 
hert  and  Carnot,  adopting  lor  the  plan  of  their  enceintes  the 
polygonal  system  with  flanking  capomtieres,  communing  with 
these  numerous  casemates  for  defence,  for  bomb-proof  shelters, 
for  quartering  the  troops,  and  preserving  the  munitions  and 
other  Ston  S. 

573... From  what  has  l»een  published  on  this  subject  l>y  the 
G  rman  engineers  themselves  and  other  BSuvopean  Writers,  the 
following  appear  to  be  the  leading  feature.-  upon  which  these 
work.-  are  based  : 

Let,  To  occupy  the  principal  assailable  points  of  the  position 
to  be  fortified,  by  works  whicb  shall  contain  within  them- 
all  the  resources  for  a  >  defence   l>y   their  garrit 

the~e  works  being  placed  in  reciprocal  defensive  relations  with 

that   the  tailing  of  one  ,,f  them 
into  the  :l  neither  oompel  the  loss  of  the. 

others  oor  the  surrender  of  the  position. 

kj«l.  To  cover  the  space  to  the   rear  of  these   ind< 
works,  cither  by  a  continuous  usually  of  the  poly- 

-tern,  with  -.i  'licient    I 

core  it  from  escalade  :  the  parts  of  tl  com- 

bined with  the  indep<  tidem 
the  icli,  both  during  the  i  distant  de- 


L81  KI.MNT    oIKMW     Fc'KTini'ATIi'N-. 

fence,  shall  be  Bwepl  in  the  most  effective  manner  by  their 
fire;  or  else  to  connect  these  works  by  long  curtains ;  or,  final- 
ly, t<»  employ  these  works,  as  in  a  system  of  detached  works, 
cither  to  occupy  important  point;-  in  advance  of  the  main  work 
or  for  forming  capacious  entrenched  camps  with  a  view  to  the 
tnalities  of  a  war.* 

3d.  To  provide  the  most  ample  means  for  an  active  defence 
by  covered-ways  strongly  organized  with  casemated  redoubt*) 
and  with  spacious  communications  between  them  ami  the  in- 
terior for  soi-ties  in  large  bodies. 

4th.  So  tx> organize  the  artillery  tor  the  near  defence  that  it 
shall  he  superior  to  that  of  the  besiegers  at  the  same  epoch} 
and  lie  placed  in  positions  where  it  will  be  sheltered  from  the 
besieger's  guns  up  to  the  time  that  it  is  to  be  brought  into 
play. 

574-...PlAjST;  The  plan  of  the  independent  works  may  be  of 
any  polygonal  figure  which  is  best  adapted  to  the  part  as- 
signed them  in  the  defence  of  the  position;  but  they  are  gen- 
erally in  the  form  of  lunettes,  PI.  23,  Fig.  2,  having  a  revetted 
scarp  and  counterscarp  to  secure  them  from  escalade.  In  the 
gOrge  of  the  work  a  casemated  defensive  barrack  is  placed, 
which  serves  as  a  reduit  or  keep;  a  simple  loop-holed  wall, 
which  is  flanked  by  the  barrack,  closing  the  space  between  it 
and  the  thinks  ot  the  work,  and  securing  the  latter  from  an  assaidt 
in  the  rear.  The  ditches  of  the  work  art'  either  flanked  from 
the  enceinte  in  their  rear,  or,  when  the  work  is  a  detached 
one,  by  oaponnieres,  or  counterscarp  galleries.  The  work  is 
Usually  organized  with  a  covered-way,  having  one  or  more 
ea.-ematcd  redoubts,  and  a  system  of  mines  both  tor  the  exte- 
rior and  interior  defence. 

575. ..The  barrack  is  usually  arranged  for  two  or  three  tiers 
of  covered  fire,  ami  an  upper  one,  with  an  ordinary  parapet 
and  tenvplein,  on  which  the  guns  are  uncovered  and  destined 
for  the  distant  defence.  The  two  upper  tiers  of  covered  tire 
are  for  artfllery,  to  sweep  the  interior  of  the  work,  and  to 
reach,  by  curvated  tires,  the  approaches  on  the  exterior.     The 


utiM    <;:  i:man    hiktti-k IATIOKB.  183 

lower  tier  is  loop-holed  for  musketry  to  sweep  the  Interior, 
The  barrack  is  surrounded  by  a  narrow  ditch  on  tin-  interior, 
and  this,  when  accessary,  is  flanked  by  small  caponni&res 
placed  in  it,  which  are  entered  from  the  lowest  story;  The 
barrack  communicates  with  the  interior  by  a  door  at  some 

suitable  point:  and  the  coniniunication  between  the  interior 
of  the  work  and  the  exterior  is  through  doors  in  the  wall  en- 
closing the  gorge. 

5'7G... Considerable  diversity  is  shown  in  the  profiles  of  th 
works.  They  usually  consist  of  a  parapet  and  rampart,  of 
ordinary  dimensions,  for  the  uncovered  defence;  of  scarps 
either  partly  detached  and  loop. holed,  with  a  corridor  between 
them  and  the  parapet;  or  of  scarps  with  relieving  arches  ar- 
ranged with  loop-holes  for  musketry;  or  .of  a  combination  of 
these  two.  The  height  of  the  barrack,  and  the  command  of 
the  paTapei  of  the  exterior  work  are.  so  determined  that  the 
masonry  of  the  former  Bhall  be  perfectly  covered  from  the 
direct  lire  of  artillery,  and  the  exterior  be  perfectly' swept  by 
the  artillery  of  the  work.  The  portions  of  the  counterscarps 
at  the  salients  are  also  arranged  with  defensive  galleries  to 
sweep  the  ditchei — usually  with  musketry,  but  in  some  cases 
with  artillery. 

r»77... In  the  salient  angles  of  the  work  casemates  are  ar- 
ranged tor  mortars,  to  fire  in  the  direction  of : the  capitals :  and 
one  or  more  easemated  traverses  are  placed  on  the  terreplein, 
to  obtain  a  fire  on  the  exterior  and  to  cover  the  terreplein 
from  ricochet.  The  masonry  of  these  traverses  is  masked  by 
the  parapet. 

rns  lead  from  the  interior  of  the  work  to  the 
;>  galleries,  the  corridors,  the  ditch  capoanieres  and  the 
mated  mortar  battery  in  the  salient. 

579.. .The  Bystem  of  mines  for  the  exterior  defence  coi 
simply  of  listening  galleries  leading  outward  from  the  oounter- 
rp    gallerii  8.     That    for    interior    defence    is    similarly    ar- 
ranged; the   communications 'with   it   being  either  from   the 
barrack  caponnien  -  or  from  the  counterscarp  of  its  ditch. 


580... The  work  is  provided  with  powder  magazines,  which 
arc  placed  at  the  points  of  the  interior  least  exposed  t<>  the 
enemy's  fire;  and  covered gaard-rooms, store+rooms for  mining 
tools,  etc.,  are  made  in  connection  with  the  posterns. 

5S1 ...  Pi:'  ii-  ir.i  s.  Tn  the  profiles  of  their  works,  the  German 
engineers  follow  nearly  the  Bame  rules  for  the  formB  and 
dimensions  of  their  parapets  as  those  in  general  use  in  other 
services.  They  employ  three  kinds  of  scarp  reveteraeuts :  1st, 
the  Ordinary  full  revebement,  PI.  20,  Fig.  1,  or  sustaining 
wall,  with  counter-forts^  2d,  reveteraents  with  relieving  arches, 
PL  21)  Figs.  1,  2,  cither  with  or  without  defensive  dispositions, 
as  circuni-tances  may  demand;  3d,  Bcarp  walls,  either  partly 
or  wholly  detached  from  the  rampart  and  parapet.  In  all  of 
these  cases,  they  give  to  their  scarp  walls  a  height  from  27  to 
30  feet  for  important  works,  and  about  L5  feet  for  those  less 
so.  The  hatter  of  these  walls  is  usually  one  base  to  twelve 
perpendicular.  For  the  full  revetement  with  counter-forts, 
thev  regulate  the  dimensions  of  both  so  as  to  afford  the  same 
stability  as  in  the  revetements  of  Tauban. 

582. ..In  their  reyeteinents  with  simple  relieving  arches,  they 
use  either  one  or  two  tiers  of  arehes  ;  placing  the  single  tier 
either  near  the  top  or  toward  the  middle  of  the  wall,  according 
to  the  nature  of  the  soil  and  the  pressure  to  be  sustained. 

58o...  Revetements  with  relieving  arehes  for  defence,  or  scarp 

galleries,  are  arranged  for  one  or  two  tiers  of  fire.  The  back 
of  the  gallery  is  sometimes  left  open',  the  earth  falling  in  the 
natural  slope  in  the  rear  ;  or  it  is  enclosed  either  with  a  plane 
Of  a  cylindrical  wall,  according  to  the  pressure  to  be  sustained. 
584... When  the  upper  part  of  the  wall  is  detached,  PL  20, 
Fig.  7,  to  form  a  corridor  between  it  and  the  parapet  in  its 
rear,  the  top  portion  alone  is,  in  some  cases,  arranged  with 
loop-holes  and  arcades,  or  with  recesses  to  their  rear,  to  cover 
the  men  from  .-hells:  in  others,  a  scarp  gallery  is  made  below 
the  floor  of  the  corridor  to  give  two  tiers  of  fire.  The  corri- 
dors are  from  8  to  20  feet  in  width,  and  when  deemed  requisite! 


Ki:<  1  \  1    oIKM  \N     1  oktifK'ATIONS.  1  s"» 

they  are  divided,  from  distance  to  distance,  by  transverse  loop* 
holed  traverse  walls  for  defence. 

585. ..When  the  scarp  calls'  are  entirely  detached,  PI.  20, 
Figs.  4,  5,  0,  they  are  arranged  for  either  one  or  two  tiers  of 
fire,  with  arcades  to  cover  the  men  ;  the  banquette-tread  of  the 
upper  tier  of  loop-holes  resting  on  the  arches  of  the  lower  tier 
of  arcad 

586. ..The  counterscarps  are  revetted,  cither  with  the  ordinary 
wall,  or  arranged  with  a  defensive  gallery,  with  a  full  centre 
arch,  parallel  to  the  face  of  the  Counterscarp  wall. 

-7. ..The  German  engineers  make  a  liberal  use  of  bomb- 
proof casemates  for  mortar  and  gun  batteries.  The  former  are 
either  placed  in  the  rear  of  the  parapet,  or  of  the  rampart,  and 
along  the  faces,  or  else  in  a  salient  angle.  In  the  former  i 
they  are  cov<  red  in  front  by  the  parapet,  in  the  latter  either 
by  the  scarp  wall  alone  or  by  a  easemated  defensive  ma.^k 
placed  in  front  of  the  battery.  When  placed  alon^  a  face,  PI. 
•J".  Fig.  '.»,  they  are  arranged  for  one  or  several  mortars,  and 
frequently  with  two  tiers  of  arches,  the  upper  one  for  the  - 
vice  of  the  mortar  and  the  lower  one  for  a  bomb-proof  shelter 
for  troops  or  munitions.  The  chamber  occupied  by  each  mor- 
tar is  a  rectangle,  L2  feet  wide,  and  about  20  feet  in  depth; 
this  i^  covered  by  a  full  centre  mmparl  arch,  the  height  of  the 
piers  at  the  back  of  the  chamber  being  -1  feet,  and  in  front  from 

o'  to  !<  feet  above  tin;  level  of  the  mortar  platform.  This  ena- 
ble- the  -1,.  d  t,.  clear  the  top  of  the  parapet  in  trout,  which  i.> 
about  12  feel  above  the  level  of  the  platform,  and  21  feet  in 
front  of  the  battery.     The  chamber  is,  in  some  easeB,  hit  open 

both  in  front  and  rear,  to  allow  the  smoke  to  escape  readily 
and  to  diminish  the  effect  of  the  concussion  of  the  discharge  on 
the  masonry;  in  other  cases  it  Is  closed  by  a  wall  in  the  rear — 
an  opening  being  left  in  this  wall,  immediately  under  the 
arch,  tor  the  same  purpose.  A  -mall  ditch  is  placed  in  front 
of  the  batten  ;  and  the  wall  in  front  L£  extendi  d  about  .'; 
above  the  platform,  I  r  the  in<  n  from   the  i 

-   that    may   fall   into   the  ditch.     The  abutments  ot 
H 


L86  KHIM     GSSKAfi     ImKUKKATIONS. 

arches  are  7  feet  thick,  and  the  piera  -1  feet.  The  arches  are  9 
feet  6  inches  thick ;  they  are  covered  on  top  by  from  4  to  ''< 
feet  in  thickness  of  earth.;  and.  in  Like  manner,  the  arch  and 
abutment  are  secured  «>n  the  side  exposed  to  an  enfilading  fire* 
An  ordinary  traverse  is  placed  on  the  same  side,  to  cover  the 
masonry  ami  communication  between  the  front  of  the  battery 
and  the  parapet ;  the  chambers  <>f  the  mortars  are  entered  from 
the  front,  or  from  the  sheltered  side,  by  a  door  in  the  abut- 
ment.   . 

588.. ."When  placed  in  an  obtuse  salient,  PI.  21,  Figs.  •'•.  1. 
behind  a  scarp  with  a  corridor,  a  space  of  10  or  12  feet  is  left 
between  the  back  of  the  scarp  wall  and  the  front  of  the  bat- 
tery. The  platfbrms of  the  mortars  are  about  the  same  distance 
below  the  top  of  the  scarp.  The  arches  are  covered  by  tho 
earth  of  the  parapet,  to  the  depth  of  5  or  6. feet.  The  dimen- 
sions and  arrangement  of  the  chambers  and  arches  are  the 
same  in  this  as  in  the  preceding  case.  The  communication 
from  the  interior  of  the  work  to  the  battery  is  by  a  postern,  'I 
feet'in  width.  ■  A  casemated  guard-room  is  made  in  connection 
with  the  postern  ;  and  when  the  scarp  is  arranged  with  reliev- 
ing arches,  either  for  defence,  or  tbr  other  purposes,  an  arched 
stairway  is  in  some  cases  made  as  a  communication  from  the 
postern  to  the  casemates.  A  transverse  wall  with  a  door-way, 
serves  to  cut  off  the  court  in  front  of  the  battery  from  the  cor- 
ridor to  the  rear  of  the  wall. 

5S9... In  the  less  obtuse  salients,  the  front  of  the  battery  is 
made  circular  ;  the  chambers  being  so  placed  that  the  fire  of  the 
mortars  can  be  thrown  in  the  direction  of  the  capital.  A  case- 
mated  defensive  traverse,  placed  in  the  salient,  masks  the  bat- 
tery in  front,  and  it  is  covered  on  the  flanks  by  the  earth  on 
the  top  of  the  arches.  The  details,  otherwise,  are  the  same  as 
in  the  preceding  ease. 

590.. .In  the  arrangement  of  casemated  traverses  for  guns. 
PI.  20,  Figs.  10,  11,  12,  the  chamber  for  each  gun  is  a  reOH 
tangle,  24  feet  in  depth,  estimated  from  the  interior  crest  of 
the  parapet,  and  12  feet  wide.     The  chamber  is  covered  by.  a 


RECK NT    ol.KMAN    K(  (IM'IKK  A  HOSTS.  187 

full  centre  arch,  the  height  from  the  level  .if  the  platform  to 
the  crown  of  the  arch  heing  S£  feet.  The  arch  is  2  feet  thick, 
the  piers  between  the  arches  3  feet,  and  the  abutments  ;>>i  feet. 
The  mask  wall  in  front  of  the  chamber  is  3  feet  thick.  This 
wall  is  covered  in  front  by  the  parapet,  ami  by  several  layers 
of  fascines  or  of  heavy  timber,  laid  across  the  embrasure  in 
the  para] iet  and  above  the  one  through  the  mask  wall.  The 
cheeks  of  the  em braaure  in  the  parapet  are  likewise  revetted 
with  heavy  timber,  to  some  distance  in  front  of  the  mask  wall. 
The  masonry  is  covered  on  top  and  on  the  sides  with  5  or  8 
feet  thickness  of  earth,  to  secure  it  from  shells  and  enfilading 
shot.     The  casemates  are  left  open  to  the  rear. 

&l...In  some  cases,  a  blinded  battery  for  a  single  gun,  PI. 
20,  Fig.  12,  is  arranged  by  enclosing  the  sides  and  front  of  the 
chamber  with  wails,  and  covering  it  with  a  layer  of  heavy- 
timber,  BUpporting  two  thicknesses  of  large  fascines,  covered 
with  a  thickness  of  5  or  6  feet  of  earth.  The  dimensions  of 
the  chamber  are  the  same  as  in  the  preceding  ease. 

592M,Xhe  caponnieres,  IM.  21,  Figs.  s.  :*.  L0,  fortflanking  the 
main  ditch. 'usually  consist  of  two  faces  and  two  caseinated 
Hank  batteries  of  two  stories  each  ;  the  lower  story  being 
loop-holed  for  musketry  and  the  upper  pierced  for  artillery. 
Each  battery  consists  of  several  rectangular  chambers,  each 

chamber  for  a  single  gun  being  1  -J  feet  wide  and  24  feet    deep, 

or  of  smaller  dim  i,  according  to  the  cali5*e  of  the  gun 

and  the  kind  of  i  on  which  it  is  mounted.    The  upper 

chambers  are  covered  with  bomb-proof  arches,  the  lower  one 
by  arches  of  sufficient   strength   tor  the  weight  thrown  upon 

them.      The  front  mask  wall  of  the  es  is   <i   feel    thick; 

the   wall    in    rear  is  3  feet   thick,  and   is  pierced  with  wind 
for    light    and    ventilation.     Openings    for    the   escape  of    the 
.e  arc  also  make  in  the   front    nia.-k   wall,  immediately    be- 
low the  crown-  of  the  arches.      An    interior  court    80   feet  in 
width  is  left  between  tl  Lank  batfc  d  when  the 

batteries  are  d<  tached  from  the  scarp  wail,  t: 


1  88  Kl  01  N  1    i.IKMAN    1  OETIFIOATK 

is  enclosed  by  a  loop-holed  wall  built  on  each  si<lo  in  the  pro- 
longation of  tin-  front  mask  wall. 

593. ..The  face-  <>f  the  caponniere  form  a  salient  of  00°. 
They  are  separated  from  the  flanks  by  two  stories  of  arched 
corridors,  in  front  of  which  arc  two  arched  chambers  of  two 
stories,  the  upper  chamber  being  arranged  for  mortars.  An 
open  triangular  court  is  left  between  the  front  walls  of  these 
chambers  and  the  faces  of  the  caponniere.  The  upper  part  of 
the  walls  of  the  faces,  along. this  court,  arc  arranged  with  ar- 
cades and  loop-holed  for  musketry,  ami  have  an  open  corridor  in 
their  rear  on  the  same  level  as  the  chambers  of  the  second 
story. 

594.. .The  caponniere  is  provided  with  a  power  magazine  find 
other  necessary  conveniences  for  the  defence. 

595.. .The  flanks  of  the  caponniere  and  its  interior  are  BWept 
by  the  musketry  of  the  scarp  galleries  in  it*  rear.  The  faces 
in  like  manner  are  swept  by  artillery  and  musketry  in  ca.-e- 
mates  behind  the  scarp. 

The  arched  chambers  of  the  upper  story  arc  covered  by  a 
thickness  of  5  or  6  feet  of  earth. 

596...Caponnieres  of  smaller  dimensions,  termed  hastiormets^ 
PI.  22,  Fig.  1,  placed  at  the  angles*  of  redoubts  to  flank  the 
ditches,  are  usually  arranged  for  mnsketvv,  but  sometimes  re- 
ceive artillery.  Those  for  flanking  the  ditches  of  the  indepen-* 
dent  works  iitffulvance  of  the  enceinte  are  sometimes  placed 
in  the  ditches  of  these  works,  sometimes  behind  the  scarp  wall 
of  the  enceinte,  and  sometimes  in  casemates  in  the  main  ditch, 
detached  from  the  scar})  wall. 

597. ..The  communications  from  the  interior  with  thecapon- 
nieres  are  by   posterns. 

598. ..The  defensive  barracks,  PI.  21,  Figs.  G,  7,  forms  one  of 
the  most  distinctive  features  in  the  organization  of  the  Ger- 
man fortifications.  The  plan  of  these -works  may  lie  of  any 
figure  to  suit  the  object  to  be  subserved  by  them.  When 
placed  in  the  gorge  of  an  independent  work  and  serving  as  a 
keep  to  it,  their  plan  is  usually  semicircular. 


BBCEBTT   (;r,i:MAN    F0BTIFICATI0N8.  189 

599. ..The  barrack  consists  of  one  or  two  stories  of  arc-hod 
ehatnbers  for  covered  fire  and  an  open  battery  on  top,  with  an 
earthen  parapel  and  terrepleim 

600...The  arched  chambers  arc  formed  by  connecting  the 
front  and  rear  walls  of  the  barrack  by  transversal  walls,  which 
serve  as  piers  for  the  arches  of  the  ceiling,  the  soffits  of  which 
arc  either  cylindrical  or  conoidal,  according  as  the  piers  are 
parallel  or  otherwise  The  chambers  are  about  18  to  20  feet 
wide  and  60  feel  in  depth  ;  their  height,  under  the.  crown  of 
the  arch,  from  9  to  11  feet.  The  arch  of  the  highest  chamber 
is  2-£  feet  thick,  and,  being  covered  with  a  capping  and  the 
earth  of  the  open  battery  on  top,  is  bomb-proof;  the  arches  of 
the  lower  stories  are  1 .1  feet  thick.  The  front  wall  of  the  bar- 
rack is  usually  6  feet,  and  is  pierced  in  each  chamber  with  one 
embrasure  and  two  loop-boles.  The  rear  wall  is  3  feet  thick, 
and  has  a  window  in  each  chamber  for  light  and  ventilation. 
Openings  for  ventilation  are  also  made  in  the  front  wall,  just 
beneath  the  crowns  of  the  arches.  Door-ways  are  made 
through  the  transversal  walls  to  form  a  communication  between 
all  the  chandlers.  These  are  sometimes  placed  along  the  cen- 
tre of  the  piers,  at  others  near  their  extremities,  so  that  the 
chambers  being  divided  by  slight  partitions  into  two  compart- 
ments, for  the  quartering  <«f  the  troops,  there  will  be  a  contin- 
uous hall  either  along  the  centre  or  near  the  rear  wall,  upon 
which  all  the  apartments  open.  The  barrack!  are.  other? 
arranged  with  all  the  requisites  for  lodging  the  troopt  comfort- 
ably and  healthfully.  The  lower  story  of  the  barrack  is  sur- 
rounded by  a  narrow  ditch,  A  drawbridge  across  this  ditch 
ires  the  entrance  to  the  barrack  at  the 

OOlt.Jn  some  cases,  PI.  21,  Fig.  .">.  where  the  front  wall  of 
the  barrack  is  much   exposed   to  the  besi<  fire,  thep 

made  thicker  oear  the»froat  wall ;  and  they  each  have  two 
vertical  grooves  to  n  seive  timber,  laid  horizontally,  betw< 
which  sand)  b*  packed  in  to  afford  shelter   when 

front  wall  has  become  much   damaged  by  tin  rtil- 

lel'Y. 


190  FRONTS    OF    P081 

602r..The  foregoing  summary  description,  with  the  plates, 
will  give  a  good  general  ides  of  the  principal  defensive*  a*- 
rangement8,  constructed  of  masonry,  which  enter  »o  largely 
into  the  recenl  German  fortifications,  and  upon  the  details  of 
which  tlic  German  engineers  have  bestowed  great  attention. 

608... The  adoption  of  the  polygonal  system,  with  capouniere 
defences  for  the  main  ditch,  lias  enabled  the  ( German  dngineeji 
to  give,  in  their  fortifications,  a  greater  exterio*  Bide  than  in 
the  bastioaed  system  generally,  and  still  admit  of  lines  of  »h'- 
fence  in  which  grape,  canister  and  small  arms,  particularly 
tlic  later  improved  musket,  will  tell  with  efficacy  upon  the 
besieger's  works  on  the  glacis  around  the  salients  of  the  en- 
ceinte. With  a  few  exceptions,  nothing  of  a  very  reliable 
character  has  heen  published  as  to  the  trace  of  these  works, 
further  than  the  general  defensive  dispositions.  From  these  it 
appeals  that,  keeping  in  view  the  cardinal  point  in  all  fortifi- 
cation, the  adaptation  of  the  various  fronts  to  the  site  of  the 
work,  so  that  all  the  approaches  upon  them  shall  be  com- 
nianded  and  swept  by  their  tires,  whilst  the  principal  lines  of 
the  enceinte  receive  the  best  direction  to  place  them  as  little 
as  possible*  within  the  range  of  enfilading  positions,  the  exte- 
rior side  is  usually  kept  somewhere  between  400  and  000 
French  metres,  or  between  450  and  700  yards. 


FRONTS  OF  T0SEN. 


604...The  following  is  an  outline  of  4hc  trace  and  defensive 
dispositions  of  a  front  of  the  fortifications  of  Posen,  one  of  the 
most  noted  of  these  recent  structures.     The  exterior  side,  A 


FRONTS    OF    POB]  ».  101 

B,  PI.  22,  Fig.  2,  is  580  yards;  B  distance,  CY>=1-15  vl  A', 
is  set  off  on  the  perpendicular  of  the  front  and  within  it;  and 
on  the  line  joining  the  salients,  *-l,  A*,  with  F.  distances,  A  IT, 
B  J/,  equal  !-<»  A  /!.  being  set  off  '/wr  the  faces  of  the  front. 
The  salient,  A',  of  the  independent  work  is  on  the  pcrpeu- 
dieular  of  the  front,  and  at  a  distance  from  £7  espial  to  ^  A  />'. 
Describing  from  A' an  are  with  a  radius  of  20  yards,  aild  draw- 
ing tangents,  to  it  from  the  joints  //"and  M.  gives  the  counter* 
scarps  of  the  independent  work  J  the  feces,  A"  F.  A'  F\  are 
parallel  to  the  counterscarp,  and  equal  to\AB.  The  ditches 
<>t'  this  work  are  flanked  by  casemated  caponnieres,  ///,  J/iV, 
which  arc  35  yards  in  length,  or  sufficient  for  four  guns.  The 
directions  of  tlu  »e  flanking  casemates  being  nearly  perpendicu- 
lar to  the  directum  of  the  faces  A/  /•'.  E  F.  The  flanks,  F  <.\ 
F  <r\  receive  the  most  snitahle  directions  for  sweeping  the  ap- 
pro aches  in  advance  of  the  salients  of  the  front.  The  main 
ditch  is  about  30  yards  wide,  its  counterscarp  being  parallel  to 
the  faces  of  the  enceinte,  and  the  gorge  of  the  independent 
Work  is  on  the  prolongation  of  this  counterscarp.  The  cur- 
tains of  the  enceinte  are  directed   from  the  points  A    V.  on  the 

point  (\  and  are  thus  nearly  parallel  to  the  exterior  side.  The 
main  ditch  is  flanked  by  a  la:  natedV defensive  barrack, 

having  three  stories  of  covered  lire,  the  lower  for  musketry 
and  the  upper  for  artillery,  and  an  open  battery  on  top.  The 
plan  of  this  work  is  that  of  the  letter  F:  the  circular  partpro- 
jects  within  the  independent  work,  and  *  its  keep ; 

side.-  are  nearly  perpendicular  to  the  faces  of  the  enceinte  and 
are  prolonged  within  the  enceinte,  serving  as  a  defensive  capon- 
niere  to  Hank  the  main  ditch,  to  sweep  the  terrepleins  of  the 
enceinte   curtains,   and    also   the    interior,   within    the   ran- 

the  guns  of  two  round  sowers  with  which  th<  ■••  term!- 

Mb  d.  The  Bides  of  the  barrack  are  separated  from  the  ram- 
part   of  the   curtain    by   lateral    ditches    1<>   yard.-  wide.  Which 

to  the  main   ditch  from  the   interior  for  troops 
large  bodi<  -  for  sorties.    1  I   of  the  •  I ' 

-  thrown  hack  from  the  scarp,  leaving   ■  corridor 


102  PSOITIS    "I     POSES. 

• 

twees  the  foot  of  its  exterior  slope  and  the  BCarp  wall,  the 
floor  of  which  i.-  L2  feel  above  the  bottom  «>t'  the  main  ditch. 
The  scarp  wall  rises  1''-  feci  above  the  level  of  the  floor,  thus 
giving  it  a  total  height  of  B8  feet  above  the  bottom  of  the 
main  ditch.  This  wall  is  loop-holed  for  small  arms.  The 
counterscarp  wall  of  the  main  ditch  is  24  feet  in  height.  The 
faces  and  thinks  of  the  enceinte  have  a  relief  of  41  feet;  the 
relief  of  the  curtain  being  only  4ft  feet.  '  The  corj-idors  of  the 
curtain  terminate  at  the  court  or  open  space  behind  the  think- 
ing easejnatcs,  7/7,  M N.  Posterns  lead  from  the  interior  to 
the  corridors  of  the  faces  and  Hanks,  and  from  the  lateral 
ditches  to  the  corridors  of  the  curtain.  The  interior  open 
space  between  the  sides  of  the  defensive  barrack  is  closed  by. 
a  loop-holed  wall  between  the  end  towers.  \  ditch  surrounds 
the  towers  and  the  gorge  between  them,  across  which  a  bridge, 
terminated  at  the  wall  by  a  draw,  gives  access  to  the  interior 
open  space  and  the  barracks. 

605. ..The  scarp,  rampart  and  parapet,  PI.  22,  Fig.  5,  of  the 
independent  work,  are  arranged  with  a  profile  similar  to  that 
of  the  enceinte.  The  circular  portion  of  the  defensive  barrack 
which  serves  as  the  keep,  is  surrounded  by  a  ditch,  "which  is 
swept  by  small  capoiinicres  attached  to  the  keep.  A  circular 
mortar  battery,  covered  in  front  by  a  casemated  traverse,  is 
placed  in  the  angle  of  this  work,  and  behind  this  a  casemated 
battery  for  howitzers  is  placed  on  its  terreplein,  in  the  direction 
of  its  capital,  to  give  reverse  views  on  the  glacis  of  the  col- 
lateral independent  works.  The  gorge  of  this  work  is  closed 
by  a  loop-holed  wall  which  extends  between  the  keep  and  the 
scarp  wall  of  the  flanks.  The  communication  between  the 
main  ditch  and  the  interior  is  through  a  gate-way  in  this  wall. 
Posterns  lead  from  the  interior  to  the  corridors  of  the  faces 
and  flanks,  and  to  the  mortar  battery  in  the  salient. 

r»oi;...The  counterscarp  of  the  independent  work  is  arranged 

with  a  defensive  gallery,  with  which  a  system  of  mines  tor  the 

■rior  defence  is  connected.     A  system  of  mines  for  the  in- 


I'OKI     AI.I.X  ANDl-.K.  lit.'; 

terior  defence  is  connected  with  the  small  caponnieres  in  the 
ditch  of  the  keep. 

607. ..The  covered-way  is  without  the  usmal  traverses,  its  in- 
terior crest  being  broken  into  a  cremaillere  line.  Its  salient 
ami  reentering  places  of  arms  are  occupied  by  casemated  re- 
douhts.  The  communications  from  the  main  ditch  to  the 
covered-way  are  by  wide  ramps,  which  are  at  the  gorges  of 
the  reentering  places  of  arms,  and  under  the  tire  of  theii 
redoubts. 


FORT   ALEXANDER. 


60d...Among  the  most  reliable  of  the  traces  published  of 
German  fortification,  is  that  of  the  main  front  of  Fort  Alex- 
ander, a  detached  quadrilateral  work  of  the  fortification.-  c£ 
Coblents,  gives  in  the  description  of  these  fortifications  by 
•  Humphrey. 

609...Plaj6*.  The  exterior  sides  of  the  enceinte  of  this  fort, 
1M.  22,  I  nn  a  parallelogram,  the  acute  angles  of  which 

are  v-">  .  The  main  and  rear  front-  arc  each  500  yards,  and 
the  other  two  420  yards  each.  The  main  front  is  of  the  poly- 
.1  .system,  with  a  strong  defensive  caponniere  to  flank  the 
main  ditch.  The  caponniere  is  covered  by  a  demilune,  and 
th^  salients  of  the  enceinta  by  counter-guards ;  the  ditch 
these  works  being  flanked  by  casemated  batl 

ring  formed  between  them.     There  is  no  covered-way  hi 
front  of  these  outwork-,  their  counterscarps  beii  tilth, 

with  a  gentle  slop.'.     \  small  earthen  work,  containing  a  i 
mated  redoubt,  is  thrown  up  at  the  salients  of  the  counter' 
guard  counterscarp. 
25 


194  FORT   ALEXANDER. 

610. ..To  construct  the  trace,  take  a  5=500  yards,  for  the  ex- 
terior side  of  the  enpeinte,  which  divide-  into  three  equal  parts, 
a  d=d  e=eb.  Bisect  a  h  by  a  perpendicular,  on  winch  sot  off 
h  JI=/<  d=h  e=l-6  a  b.  Through  //,  drawing  a  parallel  to  a 
b,  and  setting  off  along  it  the  distances  11  A  =  H  Z?sbS20 
yards,  the  points  A  and  B  will  be  the  salients  of  the  counter- 
guards. 

611. ..From  //as  a  centre,  with  the  radii  lid,  He,  describe 
two  arcs,  on  which  set  off  from  d  and  e  the  chords,  d  i=e  k~ 
33  yards,  these  will  be  the  lengths* of  the  ca.semated  flanks;  i 
k  being  joined,  gives  the  enceinte  curtain.  The  salient  angle 
of  the  main  caponniere  is  constructed  by  drawing,  from  a 
point,  m,  on  the  capital,  at  a  distance  of  20  yards  from  the 
lines,  lid,  He,  lines  to  the  extremities,  i  and  It,  of  the  case- 
mated  flanks.  The  flanks  of  the  caponniere,  t  n=v  o,  extend 
back  to  the  exterior  side,  and  are  33  yards  in  length  and  33 
yards  apart,  or  each  16£  yards  on  each  side  of  the  capital. 
The  faces  of  the  counterguards  are  directed  on  a  point,  C=i 
A  B—$?>\  yards  on  the  capital  from  //.  The  salient,  F,  of 
the  demilune  is  1-6  A  i?=106  yards  from  the  point  C;  its 
faces,  F  D,  F  E,  arc  parallel  to  the  lines  II d,  II  e,  which 
last,  joined  by  an  arc  of  a  circle,  described  from  m  as  a  centre, 
with  a  radius  of  20  yards,  and  terminated  at  the  counterscarp 
of  the  enceinte  ditch,  which  is  28  yards  from  a  b,  will  give  the 
demilune  gorge.  A  casemated  battery  for  three  guns,  behind 
the  demilune  scarp  wall,  flanks  the  couhterguard  ditch,  and 
one  for  three  guns  flanks  the  demilune  ditch,  and  closes  the 
opening  between  the  demilune  and  counterguard  at  this  point. 
A  narrow  ditch,  10  feet  wide,  is  left  between  the  flank  of  this 
battery  and  the  extremity  of  the  counterguard,  as  a  communi- 
cation between  the  main  ditch  and  the  ditches  of  the  outworks. 
This  opening  is  masked  by  an  overlap  of  the  counterguard. 

612. ..Casemated,  or  blinded  batteries^  are  made  in  the  sa- 
lients of  the  enceinte  and  of  the  demilune. 

613.. .Profiles.  The  main  caponniere,  Fig.  8,  has  two  tiers 
of  covered  artillery  fire  on  the  flanks,  of  Ave  guns  each  ;  the 


FORT    AI/KXAXDKU.  105 

lower  to  sweep  the  main  ditch,  the  upper  the  terrepleins  of  the 
counterguards ;  its  faces  have  two  tiers  of  loop-holes.  It  has 
no  uncovered  fire,  but  a  simple  covering  of  earth  as  a  bomb- 
proof. 

614.. .Casemates,  for  five  mortars  each,  are  placed  in  the  sa- 
lients of  the  enceinte,  at  the  foot  of  the  rampart  slope. 

615... A  narrow  corridor,  Fig.  0,  the  floor  of  which  is  20  feet 
above  the  bottom  of  the  main  ditch,  is  left  behind  the  scarp  wall 
of  the  enceinte;  the  faces  and  curtains  of  this  wall  are  loop- 
holed,  and  arranged  with  arcades  to  shelter  the  men,  like  the 
detached  scarp  walls  of  Carnot.  These  scarps  arc  30  feet  high. 
The  command  of  the  enceinte  over  the  parade  is  26  feet. 

616. ..The  scarp  walls  of  the  demilune  and  counterguards, 
Fig.  7,  are  arranged  Like  those  of  the  enceinte.  The  command 
of  these  works  is  16  feet.  Their  counterscarps  are  arranged 
with  loop-holed  galleries,  from  which  communications  lead  to 
a  system  of  mines  for  exterior  and  interior  defence. 

617.. .The  rear  side  of  this  fort,  not  being  exposed  to  artillery, 
is  simply  closed  by  a  loop-holed  wall  and  ditch.  A  large,  cir- 
cular, defensive  barrack  occupies  the  centre  of  this  rear  front, 
serving  as  a  keep  to  {he  fort,  and  to  sweep  by  its  fire  the 
ground  on  the  rear  and  flanks  of  the  front. 

618. ..It  will  be  seen  that,  in  the  arrangement  of  the  plan  of 
tliis  work,  the  polygonal  system,  with  caponniere  defences,  of 
Montalembert,  has  been  adopted  as  the  basis,  with  such  modi- 
fications as  the  features  of  the  site  afforded,  t<>  withdraw  the 
principal  Lines  from  the  range  of  the  enfilading  views  from 
without. 


A 


li'fi  WORK    AT   GERMEE8HBTM. 


.  WORK  AT  GERMERSIIEIM. 


G19...In  tlie  organization  of  works  with  wet  ditches,  the  Ger- 
man engineers  adopt  the  same  general  disposition  of  the  ele- 
ments of  a  front  as  they  do  in  dry  ditches;  occupying  the  moat 
important  points  of  the  polygon  to  be  enclosed  by  independent 
Works,  and  composing  the  enceinte  of  fronts  of  the  polygonal 
system?  taking  their  exterior  sides  between  the  limits  of  350 
and  050  yards,  and  sweeping  the  main  ditch,  and  the  positions 
for  the  besieger's  breaching  batteries  around  the  salients  of  the 
enceinte,  by  the  flanks  of  a  defensive  caponniere.  The  follow- 
ing concise  description  of  a  front  of  the  teU  <l<  pont  opposite 
Germersheim,  will  give  a  good  idea  Of  the  general  defensive 
arrangements  in  such  eases. 

02O...Plan.  The  front,  X  Y,  PL  33^  Fig.  1,  is  a  tenailled 
line  with  a  slight  reentering  at  the  centre  of  the  exterior  side. 
The  salients  of  the  front  are  occupied  by  small  bastions,  with  a 
scarp  gallery  on  the  faces  and  thinks,  and  having  its  gorge 
closed  by  a  loop-holed  wall,  with  a  defensive,  casemated  reduit 
at  its  centre. 

621. ..The  centre  of  the  front  is  occupied  by  a  capacious  case- 
mated  edifice,  which  extends  from  the  interior  of  the  gorge  of 
the  independent  work,  across  the  main  ditch,  to  within  the 
enceinte.  The  circular  portion  of  this  edifice,  jwithin  the  inde* 
pendent  work,  has  two  tiers  of  covered  fire,  with  an  open  bat- 
tery on  top,  and  serves  as  the  reduit  of  this  work.  The  central 
portion  has  two  tiers  of  covered  fire,  and  serves  as  a  caponniere 
for  sweeping  the  main  ditch,  etc.  Underneath  this  portion  are 
arched  passages,  to  communicate  by  water  between  the  ditch 
on  each  side  of  the  caponniere.  The  part  of  the  edifice  within 
the  enceinte  is  a  defensive  barrack,  with  three  tiers  of  covered 


WOIJK     AT    OKKMKKSUKTM.  197 

fire,  and  an  open  battery  on  top,  from  which  the  terreplein  of 
the  enceinte  curtain,  the  gorges  of  the  bastions  and  the  glacis 
of  tfie  enceinte  can  be  swept. 

622. ..The  enceinte  curtain  is  not  revetted  with  masonry. 
The  exterior  slope  of  its  parapet  descends  to  a  wide  berm  .»<v- 
eral  feet  above  the  water  level  of  the  wet  ditch,  and  which, in 
many  places,  is  planted  with  a  thorn  thickset  hedge  as  an  ol>- 
Btacle  to  an  assault.  The  rampart  of  the  curtain  is* sustained 
within  by  a  high  wall,  which  joins  the  loop-holed  walls  of  the 
bastion  gorg<  s,  and  is  flanked  by  the  baBtibn  reauits. 

623.. .The  independent  work  is  ip  the  form  of  a  lunette;  its 
faces  being  divided  into  three  parts,  each  with  a  greater  com- 
mand than  the  oneain  its  rear.  The  profile  of  this  work  is  like 
that  of  the  enceinte  curtain  ;  its  ditches  are  dry.  their  bottoms 
being  slightly  above  the  water  level  of  the  main  ditch.  The 
ditches  are  flanked  by  casemated  caponnieres  which  extend 
across  them  to  the  goTges  of  the  reentering  places  of  arms,  for 
which  works  they  al>o  serve  as  reduits.  They  are  connected 
with  the  central  rednit  by  loop-holed  walls. 

oi'4...The  covered-ways  are  without .traverses.  A  casemated 
reduit  or  traverse  separates  the  reentering  place.-  bf  arms,  on 
each  side,  from  the  coVered-ways  bf  the  enceinte  and  independ- 
ent work,  and  sweeps  them  both.  These  are  connected  by 
loop-holed  walls  in  front,  which  join  those  in  their  rear. 

625. ..The  counterscarps  of  the  enceinte  and  independent 

work  are  of  earth. 

626.. .A  passage  leads  from  the  interior  across  the  main  ditch 
on  each  sid<  •  ■'  tl  •  central  casemated  edifice,  and  extends  along 
the  counterscarp  of  the  enceinte.    This  passage  is  a  few 
above  the  water  level,  the  two  ends  being  connected  by  brid< 
across  that  portion  of  the  main  ditch  where  the  arched  Com- 
munication under  the  main  caponnien 

\  ept   by  two  small,  casemated  caponn  iiich  pro 

from  the  -  d.  -  of  the  main  caponni 

7...Iiani].s  lead  from   the  .  to  the  inte- 


1  98  WOBK   at  (.1  i:m;:k-iii.im. 

rior  of  the  independent  work  at  its  gorge,  and  to  that  of  the. 
reentering  places  of  arm* 

628.. .An  interior  ami  exterior  system  of  mines  is  connected 
with  the  independent  work  and  the  r&duita  of  the  reentering 

place  ft'  an. 

0:2!'... In  the  application  of  this  system  to  wet  ditches.,  the 
means  of. communication  between  the  enceinte  and  the  various 

outworks, .by  the  passages  and  small  bridges,  across  the  main 
ditch  and  along  the  sides  of  the  central  caponniere,  are  princi- 
pally npticeable,  as  the  other  features  do  not  differ  in  any  great 
degree  from  its  application  to  dry  ditches.  Here, one  of  the 
main  objections  to  wet  ditches,  the  difficulty  of  keeping  open  a 
communication  by  means  of  rafts  or  boats,  for  sorties  and  other 
purposes,  is  obviated  by  the  arrangement  of  the  passage  in 
question.  The  bridges,  connecting  the  break  in  this  passage, 
may  be  so  arranged  as  to  be  readily  removed  or  destroyed 
when  the  besieger  has  gained  such  a  footing  beyond  the  main 
ditch  as,  by  a  rapid  assault)  to  endanger  the* safety  oi'  the  en- 
ceinte. This  mode,  however,  of  establishing  a  foot  communi- 
cation between  the  enceinte  and  the  outworks  of  a  front,  is  not 
peculiar  to  this  system  ;  as  like  means  are  used  in  the  bastioned 
system,  by  placing  the  bottom  of  the  double  caponniere  slightly 
above  the  water  level  of  the  main  ditch,  connecting  the  two 
parts  of  this  ditch,  on  each  side  of  the  caponniere,  by  a  narrow 
ditch,  between  this  and  the  gorge  of  the  demilune  redoubt, 
over  which  a  slight  temporary  bridge  is  thrown,  so  long  as  it 
is  found  necessary  to  keep  open  this  communication. 

630.. .The  German  engineers  apply  the  preceding  dispositions 
to  every  class  of  detached  works,  whether  within  reach  of  the 
artillery  of  the  main  work  or  beyond  it.  In  the  former  case, 
the  work  is  either  in  the  form  of  a  lunette  or  a  redan,  accord- 
ing to  the  requirements  of  the  site,  the  gorge  of  the  work  being 
secured  by  a  slight,  loop-holed  wall  that  can  be  readily  de- 
stroyed by  the  artillery  of  the  place,  and  thus  open  its,  interior 
to  view  when  occupied  by  the  besieger.  In  the  latter,  the 
plan  is  that  of  a  polygonal  redoubt  enclosed  on  all  sides  by  a 


WORK    AT    GKKMIKSlll  IM.  109 

parapet.  The  ditches  in  nil  such  cases  are  flanked  by  small 
osponnieres,  placed  at   the  angles  of  the  work,  and   arranged 

both  for  musketry  and  artillery,  besides  a  counterscarp  gal- 
lery, which  serves  as  the  point  6f  departure  tor  the  galleries  of 
the  exterior  system  of  mines. 

631. ..Remarks.  The  apparently  wide  divergence  beweCn 
the  German  fort  in'  ration  of  the  present  day  and  the  bastioned 
system,  which  lasl  had  been  adopted  as  the  normal  one  thrdugh- 
out  the  world  until  these  innovations  were  practically  intro- 
duced, has  given  rise  to  active  discussions  among  engineers  in 
Europe,  in  which,  as  in  all  such  cases,  very  ultra  ground  has 
been  taken  by  both  parties  to  the  dispute.  In  each  system  the 
points  admitted  as  GBsential  in  all  fortification  of  a  permanent 
character  are  sought  for,  viz:  lsfy  an  enceinte  secure  from  es- 
calade and  thoroughly  flanked  by  artillery  and  small  arms  ; 
2d,  Mich  an  adaptation  of  the  plan  of.  the  enceinte  to  the  site 
as  shall  secure,  as  fill  as  practicable,  the  principal  lines  from 
enfilading  views  ;  .'Id,  outworks  of  sufficient  strength  in  them- 
selves, and  of  such  defensive  relations  to  the  enceinte,  as  to 
force  th  :•  to  carry  them  by  regular  approaches  before 

being  able  to  assault  the  enceinte;  4th.  interior  defensive 
works,  or  keeps  within  the  assailable  points  of  the  enceinte, 
and  in  the  outworks  first  Subject  to  an  attack,  to  give  confi- 
dence to  their  garrisons  in  holding  out  to  the  last  extremity; 
r>tli.  the  means  necessary  for  an  active  defence*  6th,  the  use  of 
mines  as  an  auxiliary  :  7th,  the  protection  of  all  masonry  by 
earthen  masks  from  the  distant  batteries  of  thi 

J. ..The  only  question  then  is.  by  which    of  these   two    ■ 

terns  the  object  in  view  '  I   attained.     Tn  the  solution  of 

.  we  are  nut  at  the  outset  by  the  ;tb-  any 

reliable  teste  as  to  the  real  value  of  t1  (op- 

ted in  th<  G  Noplace  fortified  by  thi.-  mode 

subjected  to  .  and  nothing  can.  t; 

be  with  certainty  stated  a-  to  the  degn  e  i  the   pe- 

culiar d-  lopted  may  I  ted  to  at 

■    some   experiments   made  at  "Woolwich,  England,  some 


200  WORK    A  I    ci  KM!  B8HXDC. 

years  ago,  to  test  the  practicability  of  breaching  detached 
scarps,  uke  those  of  Cannot,  when  covered  by  an  earthen  mask, 
with  heavy  guns  throwing  their  projectiles,  within  the  usual 
range  of  ricochet  fire,  over  the  earthen  mask  to  reach  the  wall 
covered  by  it;  and  others  made  at  Bapaune,  France,  on  the 
effects  of  shptondef  -.    Kiese experiments*  to- 

isr  with  Bome  facts  dmwn  from  the  sieges  in  Italy  and 
Spain*  during  the  period  between  the  first  French  revolution 
and  the  peace  of  L815,  and  the  more  recent  attacks  on  fortifi- 
cations during  tlie  straggle,  between  Russia  and  the  Allies,  go 

to  .-how  thai  all  structures  of  masonry,  whenever  they  can  he 
reached  by  heavy  projectiles  within  the  range  of  800  to  L,000 
yard.-,  whether  in  view  or  not,  may  be  greatly  damaged  it*  not 
entirely  ruined;  and  that  troops  within  defensive  casemates 
exposed  to  such  a  fire,  would  be  soon  driven  out  of  them  hv 
thc  embrasure  shots,  and  the  cannon  destroyed.  Thai  the 
flanking  cappnniereja  of  the  enceinte  and  of  the  independent. 
works  in  the  German  .systems  are  thus  exposed  and  liable  to 
these  objections,  does  not  admit  of  a  question.  Like  assertions 
may  he  made  of  the  scarps,  which  are  either  wholly  or  partly 
detached,  and  of  the  traverse  walls  by  which  the  corridors  of 
the  enceinte  are  divided  tor  defence.  The  defensive  harracks 
in  the  gorges  of  the  independent  works,  and  which  serve  as 
their  reduits,  as  well  as  the  loop-holed  wall  by  which  the  gor- 
ges of  these  works  are  closed,  being  thrown  back  from  the 
cover  of  their  parapets,  are  also  similarly  exposed.  The  Ger- 
man engineers,  it  is  said,  have,  by  the  dispositions  made  in 
some  of  their  more  recent  structures,  by  abandoning  the  conn- 
tersloping  glacis  of  Carnpt  and  his  detached  scarps,  employing 
in  their  stead,  on  fronts  of  attack,  scarps  with  relieving  arches, 
and  covering,  to  some  extent,  their  ditch  caponniere  defei 
by  earthen  masks,  shown  some  distrust  of  the  methods  mostly 
nsed  in  their  firs!  structures,  planned  upon  the  views  of  Mon- 
talemhert  and  Carnot. 

633. ..The  polygonal  trace,  which  obtains  in  most  of  the  re- 
cent German   works,  has   certain   prominent   advantages  and 


WORK    ai    <. u:\ii k-iium.  'Jul 

defects  which  may  be  seen  bv  a  slight  comparison  with  the 
bastion. m1  system.  As  the  exterior  sides  are  longer/land  the 
reenterings  of  the  enceinte  less  deep  than  in'  the  bastioned 
systems,  it  billows:  l.-t,  that  the  interior  space  enclosed  bv  the 
eaceinte  is  greater  in  the  polygonal  trace;  2d,  that  the  face-  of 
the  enceinte  arc  less  exposed  to  ricochet  from  the  greater  ob- 
tuseness  of  the  salient  angles;  3d,  that  the  fire  of  the  faces 
have  thus  a  better  bearing  on  the  distant  defence;  4th,  that, 
requiring  fewer  fronts  on  a  given  extent  of  line  to  be  fortified, 
there  will  be  fewer  flanks  and  more  artillery,  therefore)  di>- 
posable  for  the  faces  and  curtains;  5th,  that,  in  the  asnal 
mode  of  attack,  the  besiegers  will  be  forced  into  a  greater 
development  of  trenches  for  the  same  number  of  fronts.  Such 
are  the  advantages  inherent  in  this  trace. 

'!.'U...It>  defects  are;  1st,  that  the  enceinte1  having  no  other 
flanking  defence  than  the  main  caponniere,  it  will  be  exposed 
to  an  escalade  SO  SOOD  as  the  tire  bf  this  defence  is  silenced; 
id,  that  tin-  progress  of  the  b  .  during  the  last  and  most 

important  period  of  the  -  but  little  delayed,  owing  to 

the  slighter  reenterings  formed  bv  the  independent  works  in 
front  of  the  enceinte  salients. 

...,'IJli"  defects  in  the  bastioned  trace,  and  the  modes  pro- 

d   by  different   engineers   to   remedy  them,  particularly 
tlo ..-'•  of  Qaxo  and   Ohoumara,  have  been  sufficiently  dwelt 
Upon  to  show  that,  with  the   advantages   inherent  in  this  1 
of  preserving  the  means  of  flanking  the  enceinte  ditch  to  the 
last,  of  throwing  the  bastion  salient-  into  deep  reenteri 
giving  a  belter  direction  to  the  enceinte  faces  for  sweeping  the 

ind  in  advance  of  the  demilune  salient  ptible  of 

iving  all  the  mean-  of  casemated  defences,  of  a  greal 
velopment  of  flank  tire,  of  defensive  arrangements  of  mines,  of 
ample  communications  tor  an  active  defence,  and  an  extension 
of  the  exterior  side,  fortified  comrat  nsnrate  with  the  impn 
late  years  i:i  artillery  and  -mall  arm>. 

••"....In    t  Ich    have    taken   place   UDOD 

its  of   these   two  tra 


202  1. 1  KM  AX    FOKTS. 

rival  schools,  each  has  seemed  disposed  to  exaggerate  the  de- 
fects and  to  depreciate  the  advantages  of  the  system  analyzed* 
and  has  conducted  his  mode  of  attack  accordingly.  The  true 
point,  however,  as  to  the  inherent  merits  of  the  question,  does 
not  lie  in  a  comparison  of  the  means  of  resistance  of  a  bas- 
tioned  trace,  with  defective  communications  and  without  case- 
mated  defences  and  mines,  ami  that  of  the  German  sv.-tem, 
but  between  the  former,  with  these  additions,  now  regarded 
by  engineers  of  every  school  as  indispensable  to  a  vigorous  de- 
fence against  the  greatly  improved  means  of  attack  of  the  pre- 
sent day,  and  the  latter. 

637. ..The  fragility  of  masonry,  and  the  case  with  which  it 
can  be  ruined  by  distant  batteries  of  heavy  calibre,  particu- 
larly when  pierced  with  embrasures  and  loop-holes,  like  the 
.caseinated  caponnieres  and  defensive  barracks  of  the  Ger- 
man system,  must  naturally  incline  engineers  to  limit  its  em- 
ployment as  much  as  possible,  reserving  its  use  for  positions 
where  it  will  not  be  subject  to  this  exposure,  or  where  it  can 
be  so  covered  with  an  earthen  mask  that  nothing  may  be  ap- 
prehended from  the  besieger's  heavy  guns. 


GERMAN    TOUTS. 


638. ..In  their  detached  works,  or  isolated  forts,  the  German 
engineers  follow  the  same  defensive  measures  as  in  the  inde- 
pendent Avorks  belonging  to  a  continuous  enceinte.  A  strong, 
casemated  barrack,  PI.  33,  Fig.  2,  the  plan  of  which  is  either 
curvilinear  or  polygonal,  with  several  tiers  of  lire,  serves  as 
the  reduit  or  keep  of  the  work,  and  is  placed  either  within  it 
or  at  its  gorge,  according  to  the  position  to  be  occupied.     The 


GERMAN    FORTS.  203 

inferior  is  provided  with  casemates  for  guns  and  mortars, 
placed  at  the  salients  and  along  the  terreplein — frequently 
under  traverses,  when  these  are  used  to  cover  a  face  from  en- 
filading views.  The  scarp  walls  are  usually  built  with  reliev- 
ing arches,  defensive  scarp  galleries,  and  open  corridors  be- 
hind the  ap  per  part  of  the  Boarp  wall,  which  is  also  loop-holed. 
The  ditches  are  flanked  by  small  capon nie res,  placed  at  the 
angles  of  the  work,  or  along  its  faces,  and  by  loop-holed  coun- 
terscarp galleries;  and  mines  for  exterior  and  interior  defence 
are  connected  with  these  galleries  and  with  a  ditch  which 
usually  surrounds  the  keep. 

639. ..Tower  Fobts.  The  favor  with  which  the  views  of 
Montalemhert  have  been  received  in  Germany,  lias  led  to  the 
adoption  of  his  circular  casemated  towers,  both  as  isolated 
forts  and  combined  in  a  system  of  detached  Works  for  covering 
a  ^pace  to  their  rear  for  an  entrenched  camp,  as  at  lints. 
These  towers,  in  their  interior  arrangements,  are  the  same  as 
the  defensive  barrack  already  describe*!,  with  the  exception  of 
those  differences  in  the  details  of  the  construction  which  the 
difference  in  their  plans  would  call  for.  They  have  several 
tiers  of  covered  fire  for  artillery  and  musketry,  and  an  open 
battery  on  top,  the  parapet  of  which  is  either  of  earth  or  of 
masonry,  according  to  the  dimensions  of  the  tower.     In  the 

towers  at  Lintz  they  are  surrounded  by  a  ditch,  and  the  whole 

of  the  masonry  which  would  be  exposed  to  the  bes  bat- 

teries is  covered  by  a  glacis,  leaving  only  the  guns  on  top  to 
have  direct  view-  on  these  batteries,  the  second  tier  firing 
under  an  elevation  over  the  crest  of  the  glacis  mask.  The 
ditch  toward  the  interior  is  crossed  by  a  temporary  fixed 
a  drawbridge  leading  to  the  second  Btoryfof  the  tower.  The 
gun.-  of  the  top  battery  are  placed  on  a  revolving  platform, 
their  carriages  being  of  a  peculiar  construction,  t<.  admit  of 
the  axes  of  the  guna  remaining  paralh  not  to  have  their 

shot  div<  Tge  from  tl bjecl  to  he  reached,  aid.  tme 

tim<  .  ,py  as  little  spaa  .  la!   rally,  a-  will   j  for 

the  service  of  the  guns.     An  earthen  para  the  guna 


204  TIIK    ADAPTATION    OF    I'lKMANlNT    FOBUFIOATIOS 

on  the  side  exposed  to  the  besieger's  fire,  and  one  of  masonry 
toward  tlif  interior.  These  towers,  with'the  exception  of  the 
open  battery,  have  the  defects  of  divergent  fires,  common  to 
all  works  with  a  circular  plan;  and  the  open  battery  is  liable 
to  be  rendered  useless,  or  be  rained  by  a  well-aimed  shot  or 
two,  or  a  heavy  shell  felling  on  its  platform.  The  tower-with- 
out earthen  masks  can  only  be  used  with  advantage  in  j 
tions  where  it  will  not  be  exposed  to  being  breached  from  a 
distance,  and  is  a  rery  good  auxiliary  in  sea-coast  defence,  for 
points  where  the  ohject  is  solely  to  prevent  an  enemy's  Vi 
from  making  use  of  a  safe  anchorage  on  the  coast. 


THE  ADAPTATION  OF  PERMANENT  FORTIFICATION  TO  THE 
TOPOGRAPHICAL  FEATURES  OF  FRONTIERS. 


640.. .No  state,  in  the  present  condition  of  civilization,  can 
be  regarded  as  secure  from  foreign  military  aggression,  the  ac- 
cessible points  of  whose  frontiers  are  not  occupied  by  perms* 
nent  fortifications  of  such  strength  as  shall  prevent  an  enemy 
from  obtaining  possession  of  them  by  a  sudden  assault,  and 
thus  procuring  the  means  of  penetrating  into  the  interior. 
Guided  by  the  experience  of  centuries  of  wars,  and  the  daily 
increasing  facilities  which  the  improvement.-  in  the  materiel  of 
armies  and  their  transportation  afford  for  rapid  and  powerful 
offensive  operations,  the  ruling  states  of  continental  Europe 
have,  within  the  last  quarter  of  a  century,  not  only  made  every 
effort  to  place  their  frontiers  in  an  unassailable  condition,  but 
also  their  great  centres  of  population  and  wealth  in  the  in- 
terior, beyond  the  chances  of  a  sudden  attack  from  an  enemy 


TO   TIIE  TOPOGRAPHICAL   FEATUEKS    <>l     FIMN'I TEES.  205 

who  might  force  his  way  through  tlic  frontier  defences,  and 
march  rapidly  upon  them,  thus  making  these  positions  the 
rallying-pointa  whore  a  defeated  army  can  find  a  safe  resting- 
place,  until  it  can  be  reorganized  and  sufficiently  strengthened 
t<>  resume  the  offensive.  Such  seems  to  be  the  result  "at  which 
the  generals  and  statesmen  of  Europe  have  arrived,  after  the 
most  mature  and  careful  consideration  of  the  important  prob* 
lcm  of  national  defence,  during  which  the  utility  of  permanent 
fortifications  was  seriously  called  in  question  by  some  who 
pointed,  in  support  of  their  views,  to  the  very  inefficient  part 
the  great  number  of  fortified  places  had  played  in  the  wars 
Waged  by  Napoleon,  when,  hy  means  of  overwhelming  num- 
bers, he  was  enabled  to  disregard  such  places,  the  garrisons  of 
which  were  too  feeble  to  make  any  efficient  offensive  move- 
ments, until  the  defeat  of  his  adversary,  in  one  or  more  great 
pitched  battles,  necessarily  also  threw  them  into  his  possession. 
<•}]. ..In  view  of  the  arguments  bated  on  these  events,  the 
opinions  of  Napoleon  himself  should  carry  great  weight  In 
speaking  of  the  bearing  of  permanent  fortifications  in  a  defen- 
sive war.  he  says:  "If  fortresses  can  neither  secure  a  victory 
nor  arrest  the  progress  of  a  conquering  enemy,  they  can  at 
leas!  retard  it.  and  thus  give  to  the  offensive  the  means 
gaining  time,  a  most  important   advantage  in  all  warfare*." 

In  like  manner,  the  Axohduke  Charles,  of  Austria,  who  showed 

himself  one  of  the  ablest  adversaries  with  whom  Napoleon 
had  to  cope,  takes  the  ground:  "That  a  defensive  warfare  can- 
not be  systematically  and  successfully  carried  on  in  a  country 
which  is  not  provided  with  fortresses  that  have  been  planned 
and  distributed  according  to  strategical  requirements."  lake 
views  were  held  hy  the  Duke  of  Wellington,  and  it  is  proba- 
ble that  no  great  general,  from  the  earliest  period  of  military 
op-,  ral  own  to  tl  tit  moment,  I 

the  contrary.     Without  going  further  hack  than  the  t> 
contests  which  have  taken  place  in  Kurop.-  within 
years,  we  gather  tin 

We  find,  on  t;  Sorts  of  powerful 


206        Tin:  adaptation  of  pbbmaitknt  forttftcatios 

Russian  forces  paralyzed  by  the  obstinate  defence  of  a  few 
weak  fortresses,  and,  in  some  cases,  of  simple  field-works  by 
the  Turks;  on  the  other,  the  gigantic  armaments,  by  sea  and 
land,  of  France  and  England  combined,  held  at  bay  in  the 
East,  and  in  the  Black  Sea;  and.  more  lately,  the  career  of 
of  France  arrested  in  the  very  flush  of  victory,  by  the  time 
which  it  must  necessarily  have  cost  her  to  break  down  the 
barriers  which  Austria  had  placed  in  her  way  in  the  strong- 
holds of  Northern  Italy.  The  only  question,  then,  on  this 
Subject  that  remains  for  solution  by  a  state  is  in  what  way 
such  a  means  of  security  from  aggression  can  be  best  adapted 
tn  its  own  geographical)  political  and  military  status. 

642.. .In  a  country  like  our  own,  with  so  vast  an  extent  >■[' 
sea-coast  and  inland  frontier,  and  with  political  and  social  in- 
stitutions which  are  so  antagonistic  to  every  approach  to  the 
maintenance  of  a  large  standing  army  as  a  measure  of  national 
safety,  this  question  is  one  of  peculiar  importance,  both  from 
the  open  character  of  this  extensive  frontier,  and  from  the  al* 
mosl  incredible  facility  with  which,  as  in  the  late  struggles  in 
Europe,  and  in  the  contests  of  China  and  India,  considerable 
armies,  with  all  their  materiel,  can  be  concentrated  on  distant 
points  by  the  aid  of  steam, 

64o...The  want  of  military  means  of  some  of  our  immediate 
neighbors,  and  the  daily  increasing  mutual  commercial  inter- 
ests between  us  and  the  greatest  naval  power  of  the  world, 
from  whom  alone  we  have  any  serious  danger  to  apprehend 
along  our  inland  frontier,  would  seem  to  favor  the  hope  that 
the  day  may  never  arrive  in  Which  our  country  will  have  to 
provide  against  invasion  except  along  the  sea-coast;  and  we 
may,  therefore,  dismiss  from  our  consideration  any  further 
provision  against  this  eventuality  than  the  security  of  our  prin- 
cipal harbors,  naval  stations  and  commercial  marts  from  a 
naval  attack,  or  from  one  combined  with  the  descent  of  a  land 
force,  which  last,  from  the  great  resources  of  our  country  in 
men  and  ••means,  would  hardly  attempt  to  penetrate  inland  be- 
yond one  or  two  marches. 


TO  THE  TOPOGRAPHICAL  FEATUBE8  OF  FRONTIERS.     207 

644.. .Tn  the  organization  of  the  frontier  fortifications  of  a 
state,  the  points  to  be  chiefly  regarded  are  the  principal  ave- 
nues of  access  to  the  interior,  and  the  topographical  features  of 
the  frontiers,  as  they  lend  themselves,  more  #r  less,  to 
strengthen  artificial  defences.  In  conducting  an  invasion 
across  ao  inland  frontier,  the  march  of  the  enemy  must  nei 
sarilv  be  along  the  roads  that  intersect  it,  as  these  afford  the 
only  good  avenues  for  transporting  the  materiel,  etc,  of  the 
army.  The  joints,  therefore,  or  places  in  their  neighborhood, 
where  the  principal  roads  or  other  avenues  of  communication 
erosa  the  frontier,  particularly  those  which  lead  to  the  greal 
centres  of  population  and  wealth,  are  the  ones  which  neces* 
sarilv  require  permanent  defences.  No  absolute  rule  can  be 
laid  down  for  the  distribution  or  the  strength  of  such  works. 

rything  must  depend  upon  the  more  or  less  of  facilitv  pre* 
sented  to  an  enemy  for  penetrating  at  one  point  rather  than 
another,  and  of  the  ulterior  advantages  which  the  possession 
of  one  may  present  to  him  over  another. 

6  !•'».. .Rivers  and  mountain  ranges  are  the  natural  fortifica- 
tions of  states,  and.  where  they  form  the  frontiers,  they  greatly 
facilitate  the  application  of  artificial  defensive  means,  as  they 
present  but  few,  and  those,  in  general,  important  points  of  ac- 
cess. When  the  points  bf  communication  on  a  river  are  forti- 
fied, an  invading  force,  however  powerful,  cannot,  without 
ross  the  river   before  first   gaining    p  n  of 

them;  for,  even  should  a  sufficient  detachment  be  left   to  ob- 

e  and  blockade  the  fortresses,  the  main  army,  in   case  of 
'     r  any  disaster,  might  be  placid  in  bj  extremely  criti- 
cal position,  in  its  movements  to  recross  the  river,  with  I 
garrisons  of  the  fortresses  threatening  its  flanks  and  rear.     In 
offensive  operations,  fortresses  upon   a   river  frontier  form    i 
of  t!  •  .   an  army.      If  a  river  in- 

•  lie  frontier,  the   point  where  it  rr 
in    its   vicinity,  should    he    occupied    by    a    p  I    work. 

Among  such  points.  I  i  ccdiarly  he 


208  THK   ADAPTATION    OF    PERMANENT    FORTIFICATION 

held  where  a  river,  forming  the  frontier,  is  intersected  by  an- 
other  navigable  one  "which  lies  wholly  within  the  frontier. 

646. ..With  respect  to  mountain  passes,  the  main  roads 
alone  will  *reqn ire  permanent  works.  It"  the  passes  are  inde- 
pendent of  each  other,  a  work  will  be  necessary  for  each  one 
separately;  but  where  several  unite  at  the  same  point,  upon 
or  within  the  frontier,  a  single  work,  placed  upon  this  point, 
will  suffice.  Local  circumstances  will  determine  the  point  in 
each  pass  which,  occupied,  will  offer  the  greates^advantage  of 
obstructing  the  march  of  an  invading  force.  The  only  rule 
that  can  be  given  is  that,  whilst  the  position  selected  shall 
satisfy  this  condition,  there  shall  be  every  facility  of  communi- 
cation between  the  fortress  and  the  interior  for  receiving  sup- 
plies and  reinforcements.  This  rule  would  lead  generally  to 
the  selection  of  some  point  of  the  outlet  lying  within  the  fron- 
tier as  the  proper  one. 

647. ..The  number  of  fine  natural  harbors  and  roadsteads  on 
our  seaboard,  where  the  largest  fleets  can  find  a  secure  an- 
chorage at  all  seasons;  the  proximity  to  the  ocean  of  many  of 
our  most  important  cities,  towns  and  populous  villages,  by 
which  they  are  not  only  exposed  to  the  usual  dangers  of  naval 
attacks,  but  to  incursions  from  an  enemy's  land  forces;  to- 
gether wTith  the  large  rivers  which,  having  their  outlets  on  this 
seaboard  frontier,  are  navigable  for  long  distances  within  it 
by  vessels  of  the  greatest  burthen,  have  given  to  the  subject 
of  sea-coast  defences  a  particular  prominence  among  ourselves. 
The  means  of  defence  disposable  for  the  security  of  these 
points,  consist  in  permanent  works  arranged  to  meet  an  attack 
both  by  sea  and  land,  and  of  such  strength  as  the  presumed 
nature  of  the  attack  will  demand;  of  such  temporary  fortifica- 
tions as  the  exigency  of  the  moment  may  point  out;  of  mova- 
ble land  forces;  and  of  floating  defences  to  act  in  aid  of  the 
others. 

648. ..The  character  of  the  permanent  defences  will  depend 
upon  the  object  in  view.  Where  this  is  simply  to  exclude  an 
enemy's  fleet  from  the  use  of  a  harbor,  or  roadstead,  which 


TO  THE  TOPOGRAPHICAL   FEATUBEB   OF    FBONTBEfiS.  209 

offers  to  him  no  other  inducement  for  its  occupation  than  that 
afforded  by  a  Becure  anchorage,  one  or  more  small  works  of 
sufficient  strength  to  prevent  the  success  of  an  open  assault 
upon  them,  armed  witll  heavy  mortars  and  guns  with  long 
ranges,  that  can  reach  by  their  fire  every  point  where  an 
enemy's  ship  could  safely  anchor,  will  be  sufficient. 

649. ..The  points  to  be  occupied  by  these  works,  as  well  as 
their  plan,  will  depend  upon  the  natural  features  of  the  har- 
bor or  roadstead.  They  will  usually  consist  either  of  open 
works,  armed  with  guns  in  barbette  and  mortars  that  can 
sweep  all  points  of  approach  to  and  Within  the  harbor,  or  of  a 
combination  of  casemated  and  open  works.  The  gorge  of  the 
works  in  all  eases  being  occupied  by  a  casemated  tower,  of 
sufficient  Btrength  and  capacity  to  hold  a  garrison  of  sufficient 
force  to  beat  off  an  open  assault  on  the  battery  by  land,  and 
be  itself  secure  from  a  coup  cU  main.  Like  defences  will  also 
be  sufficient  for  the  security  of  the  smaller  classes  of  towns 
and  villages,  which  would  probably  oiler  a  temptation  only  to 
a  small  naval  force, 

650. ..In  the  case  of  important  commercial  cities  and  large 
naval  depots  lying  within  harbors  more  or  less  accessible  both 
to  sea  and  land  attacks,  the  character  of  the  defences  called 
for  should  be  commensurate  with  the  magnitude  of  the  inter- 
ests to  be  guarded,  and  the  consequent  temptation  to  an  enemy 
to  put  forth  great  efforts  for  their  occupation  and  destruction. 

661...The  avenues  of  approach  to  these  objects  by  sea,  which 
can  be  brought  within  range  of  cannon  and  mortars,  in  forti- 
fications on  the  shore,  or  in  works  erected  on  natural  or 
artificial  island.-,  should  be  occupied  to  a  distance  that  will 
prevent  a  fleel  from  approaching  near  enough  to  open  a  bom- 
bardment ;  and,  it'  practicable,  should  also  force  the  enemy,  if 
he  ventures  a  laud  attack,  to  disembark  his  troop-  cither  al 

•  a  distance  from   th<'  object  to  lie  reached  that  he  will  not 
he   aide,  by  a  sudden  d<  et  a  surprise,  or  to  limit 

his  lauding  to  such  point  tin  their  i 

tion,  may  render  tie  the   naval   and   land 

27 


210  THE   AHAPTATTOM   OF    11  i:M.\.\iNT   FOSTOTOATIOH 

forces  very  uncertain,  and,  in  case  of  a  storm,  place  the  latter 
in  a  very  perilous  condition  it"  attacked. 

652...  i  he  exterior  chain  of  the  defences  will  consist  of  works 
of  the  above  character;  Within  these,  batteries,  either  open 
or  casemated,  as  the  locality  may  seem  to  demand,  should 
occupy  all  the  most  suitable  positions  both  for  sweeping  tho 
path  that  a  fleet  must' follow  by  powerful  cross,  direct  and 
enfilading  fires,  and  for  reaching  every  point  of  anchorage 
within  the  harbor.  On  the  land  approaches,  points  should  be 
occupied  by  forts  of  a  permanent  character,  which  will  pre- 
vent a  sufficiently  near  approach  to  bombard  the  city  or  depbt% 
and,  in  combination  with  temporary  works,afford  an  intrenched 
field  of  battle  for  the  troops  on  the  defensive.  These  will 
form  the  exterior  line  of  the  land  defences ;  the  interior  line 
being  either  a  continuous  enceinte  of  permanent  fortification 
which  will  require  a  regular  siege  for  its  reduction,  or  else  a 
suitable  combination  of  either  continuous  or  detached  iield- 
Works  of  such  strength  and  armament  that  the  enemy,  in  any 
attempt  to  carry  them  by  an  open  assault,  will  be  made  to 
suffer  heavily,  even  if  he  is  not  repulsed.  The  security  of  ob- 
jects of  this  character  will  be  greatly  increased  when  they  lie 
at  some  distance  within  the  sea-coast  frontier,  and  can  only  lie 
approached  either  by  water,  through  such  comparatively  nar- 
row defiles  as  even  our  largest  rivers  present,  or  by  land  only 
after  one  or  more  marches.  These  defiles  will,  for  the  most 
part,  not  only  present  admirable  positions  on  their  banks  from 
which  they  can  be  enfiladed  within  the  range  of  the  heaviest 
guns,  but  frecpiently  others,  at  points  where  the  river  narrows, 
oi-  changes  its  course,  where  works,  occupying  the  opposite 
banks,  will  give  the  means  of  rendering  the  river  impassable 
by  booms,  rafts  or  other  floating  or  sunken  obstructions,  which 
cannot  be  removed  except  by  getting  possession  of  the  de- 
fences, by  which  they  are  guarded,  by  a  land  attack. 

653...  Wherever  harbors  or  hays  are  of  that  extent  that  their 
entrance  cannot  be  interdicted  to  an  enemy's  fleet,  nor  secure 
anchorage  within  them  be  prevented,  of  which  we  have  ex- 


TO   TIIE   TOPOGRAPHICAL   FEATURES    OF   FRONTIKKS.  211 

ampleson  our  coast,  the  case  falls  beyond  the  province  of  for- 
tification, and  must  be  left  to  floating  defences  for  a  solution. 
Sere  even  some  fortified  harbors  on  the  shores  of  such  exten- 
sive estuaries  may  give  secure  places  of  refuge  for  ships  of 
Avar,  from  which  they  may  at  any  moment  sally  when  they 
can  take  the  enemy  at  disadvantage,  or  into  which  they  can 
retreat  if  attacked  by  a  superior  force. 

654L..The  necessity  for  fortifications  for  the  security  of  fron- 
tiers being  admitted,  there  is  seldom  any  doubt  as  to  the  points 
to  be  occupied,  as  these  are  usually  unmistakably  marked  out 
by  nature  herself.  Of  the  character  of  the  defences  for  ti. 
points,  the  features  of  the  locality  and  the  importance  of  the 
points  themselves  to  military  operations,  either  defensive  or 
offensive,  beyond  the  immediate  range  of  their  guns,  must, 
decide.  Here  the  question  comes  exclusively  within  the  do- 
main of  the  engineer,  and  its  solution  will  be  more  or  less  per- 
fect as  he  has  the  ability  to  adapt,  in  the  best  manner,  all  the 
urces  of  his  art  to  the  peculiar  circumstances  of  the  i 
re  him. 

655...In  the  powerful  military  states  of  continental  Europe, 
the  question,  as  to  what  extent  the  great  centres  of  population 
and  wealth  in  the  interior  should  be  covered   by  fortifications, 
has  been  submitted  to  the  investigation  of  the  ablest  engineers 
and  statesmen,  from  the  time  of  Vanban  down  to  the  pn  - 
day,  but  more  particularly  since  the  fall  of  Napoleon,  a  catas- 
trophe which  mighl  not  have  taken  place  had  Paris  bee- 
cured  by  fortifications,  which  would  have  prevented  a  con 
main  when  the  armies  of  the  Allies  gained  possession  of  il 
the  resuli  of  a  pitched  battle.     Whatever  differences  of  opinion 
have  been  called  forth,  as  to  the  mode  oi  accomplishing  this 
object,  as  shown  in  the  published   views  on  the  propositioi 
fortify  Paris,  there  seems  to  have  been  none,  among tl 
lied    to  decide  upon  it,  as  to  the  great   important 
fortifying  this  capital,  and  other  large  places  in  the  hit 

which,  from  their  position,  m  the  big 

strategical    value,   in    tin 


212  THE    ADAPTATION    OF    PERMANENT    I  <  >K'l  II  k  ATIoN. 

large  army,  as  not  only  to  prevent  their  wealth  and  resom 
from  falling  into  the  possession  of  the  invading  force,  but  to 
make  them  safe  rallying-points  for  beaten  and  dispersed  for 
and  depots  for  organizing  new  armies.  The  plan  that  has  been 
adopted  for  this  end  both  in  France  and  in  most  ut*  the  other 
parts  of  Europe,  w*hich  have  been  either  newly  fortified  or  had 
their  old  works  strengthened  within  this  period,  is  to  surround 
the  city  by  a  continuous  enceinte  of  greater  or  less  strength, 
but  one  secure  from  a  oowp  dt  main;  and  to  occupy,  with 
forts  of  a  permanent  character,  the  most  suitable  points  in  ad- 
vance of  the  enceinte,  to  prevent  an  enemy  from  bombarding 
the  city,  or  penetrating  between  the  forts  without  first  gaining 
possession  of  them.  By  this  plan,  it  is  proposed  to  gain  all 
the  advantages  offered  by  the  passive  resistance  of  fortifica- 
tions, and  the  activity  of  a  disposable,  movable  force  occupy- 
ing the  zone  between  the  enceinte  and  the  forts  as  an  intrenched 
camp,  upon  which  the  forts  with  temporary  works  thrown  up 
between  them  would  render  an  open  assault  too  perilous  to 
be  attempted. 

G5G...The  enceinte  of  Paris  consists  of  continuous  bastioned 
fronts  without  outworks,  having  a  revetted  scar})  of  the  usual 
height  to  secure  it  from  escalade,  and  a  ditch  with  a  counter- 
scarp of  earth.  The  advanced  forts  are  either  quadrangular 
or  pentagonal  bastioned  works,  enclosing  all  the  means  of  se- 
curity for  their  garrisons,  as  bomb-proofs,  etc.,  their  plan  being 
skilfully  adapted  to  the  site,  and  to  their  mutual  bearing  on 
the  defence.  The  fortifications  of  Lyons  present  more  diver- 
sity, both  in  the  plan  and  details  of  the  enceinte  and  forts, 
although  the  general  system  is  the  same  as  that  of  Paris.  In 
the  last  is  seen  a  more  extensive  application  of  casemated  ami 
gallery  defences,  both  for  exterior  flanking  and  for  the  defence 
of  the  interior  of  the  forts;  growing  out  of  the  more  broken 
features  of  the  site  generally,  and  frequently  from  the  more 
coniined  space  occupied  by  them. 

(557. ..In  Germany,  the  same  general  system  of  a  continuous 
enceinte,  with  strong  advanced  isolated  works,  has  been  fol- 


SUMMAKY    OF   THE    PROGEE88   OF   FORTIFICATION.  213 

lowed,  the  whole  being  planned  and  combined  according  to 
the  distinctive  features  of  what  is  known  as  the  German  system 
of  fortification. 

658.. .In  our  own  country,  where  our  largest  centret  of  popu- 
lation and  wealth  lie  almost  immediately  upon  the  seaboard, 
it  would  seem  impracticable,  in  view  of  the  rapid  spread  of 
population  around  them,  and  the  consequent  changes  in  local 
features,  to  resort  to  any  defences  of  a  permanent  character,  to 
secure  them  from  a  land  attack,  even  were  the  nation  willing 
to  assume  the  burthen  of  the  great  outlay  for  such  an  object, 
as  in  a  few  years  the  works %f  to-day  might  be  rendered  uso- 
lesa  by  the  changes  referred  to.  Even  in  Europe,  the  strongest 
despotic  governments  have  been  obliged  to  cede,  what  seemed 
military  exigencies,  to  the  demands  of  the  social  condition, 
and  either  to  raze  the  fortifications  of  cities,  to  give  room  to  a 
crowded  population,  or  else  t<»  suffer  such  encroachments  on 
the  ground  necessary  for  the  functions  of  the  works  as  to 
rentier  thorn  nearly  useless.  The  only  defensive  resource  that 
seems  left  to  ourselves,  in  like  cases,  is  in  the  use  of  field 
works,  one  which  our  military  experience  shows  may  he  relied 
UpOll  with  confidence,  BO  long  as  the  military  aptitude  of  OUT 
population  remains  unchanged,  from  what  it  has  thus  far  been. 


SIMMY  OF  THE  PROGRESS  OF  FORTIFICATION 


9.. .The  records  of  history  and  the  vestiges  of  remote  civili- 
zation  show  that  the  art  of  fortification,  in    some  ;  an- 
other, has  been  in  practice  throughout  all  nations,  <  ven  in  the 
lowi                                       u,  and  that,  wherever  it  has  i 
cultvated,  i;              ter  has  been  mo              -  influenced,  no< 


214  sl'MMAKY    01    THE    PROGRESS    OF    l  OB  1 11-  'Ii  ATION. 

only  by  the  natural  features  of  the  country,  bul  by  the  politi- 
cal and  social  conditions  of  its  inhabitants.  In  its  earliest  ap- 
plications, we  find  men  resorting  to  one  or  mure  simple  enclo- 
sures ol  earthen  walls;  or  of  these  surmounted  bj 
placed  in  juxtaposition;  <>r  of  stakes  alone  firmly  planted  in 
the  ground  with  a  strong  wattling  between  them;  or  of  timber 
in  its  natural  state,  having  it.-  branches  and  the  undergrowth 
strongly  interlaced  to  form  an  impervious  obstruction,  with 
tortuous  paths  through  it,  known  only  to  the  defenders. 

660...A  resort  to  such  feeble  means  shows  not  only  a  very 
low  Btate  of  this  branch  of  the  military  art,  but  also  of  that  of 
the  attack,  as  defences  of  this  kind  would  present  hut  a  slight 
obstacle,  except  against  an  enemy  whose  habitual  modi'  of 
warfare  was  as  cavalry,  or  of  one  not  yet  conversant  with  the 
ordinary  plans  for  pealing.  This  class  of  fortifications  for  the 
defence  of  entire  frontiers  has  been  mostly  met  with  in  the 
east  of  Europe,  and  was,  doubtless,  at  the  time,  found  to  b 
sufficient  protection  against  those  nomadic  tribes  that  for  : 
have  roamed  over  its  vast  plains,  and  who  are  only  formidable 
as  a  mounted  force. 

'Hil. ..The  next  obvious,  and,  in  humid  countries,  necessary 
step  was  to  form  -walls  either  of  rough  blocks  of  stone  alone, 
or  of  these  interlaced  with  the  trunks  of  heavy  trees.  Ob- 
structions of  this  kind  could  only  be  used  to  a  limited  extent, 
and  were  confined  to  the  defences  of  places  forming  the  early 
centres  of  population.  As  human  invention  was  developed, 
these,  in  their  turn,  were  found  to  present  no  serious  obstacle 
to  an  assault  by  escalade — giving  to  the  assailed  only  the  tem- 
porary advantage  of  a  more  commanding  position — and  they 
gave  place  to  walls  of  dressed  stone,  or  brick,  whose  height 
and  perpendicular  face  alike  bade  defiance  to  individual  at- 
tempts to  climb  them,  or  the  combined  efforts  of  an  escalade. 
From  the  tops  of  these  inaccessible  heights,  sheltered  in  front 
by  a  parapet  of  stone,  and,  in  some  cases,  by  a  covered  corri- 
dor behind  it,  the  assailed  could  readily  keep  at  bay  any 
enemy,  so  long  as  he  could  be  attained  by  their  missiles;  but 


SUMMARY    OF   THE    PROGRESS    OF    FORI  II  l<  I  \TION.  215 

having*  reached  the  foot  of  tine  wall,  he  here  found  Bhelter 
-from  these,  and,  by  procuring  any  cover  that  would  protect 
him  from  objects  thrown  from  above,  could  securely  work  at 
effecting  a  breach  by  mining.  It  was  probably  to  remedy  this 
defect  of  simple  walls  that  towers,  which, at  first,  were  nothing 
more  tlian  square  or  semi-circular  projections  built,  from  dis- 
tance to  distance,  in  the  wall  itself,  were  first  devised.  These, 
subsequently,  were  not  only  enclosed  throughout,  but  divided 
into  stories,  each  of  which  was  provided  with  loop-hol< 
flank  the  adjacent  towers  and  the  straight  portions  of  the  wall 
between  them,  and  was  isolated  at  top  from  the  straight  por- 
tion of  the  walls  adjacent  to  it  by  a  break  or  ditch,  on  the 
interior,  between  the  towef  and  the  wall,  across  which  a  com- 
munication between  the  two  could  be  established  by  a  tem- 
porary bridj 

,  oT>2.. .These  formidable  defences  were,  in  their  turn,  found  to 
be  insufficient  against  the  ingenuity  and  skill  of  the  assailant, 
who,  by  means  of  covered  galleries  of  timber,  sometimes  above 
iii*l  and  sometimes  below,  gradually  won  his  way  to  the 
foot  of  the  wall,  where,  by  breaking  his  way  through  it,  or  by 
undermining  and  supporting  it  on  timber  props,  to  be  subse- 
quently destroyed  by  fire,  he  removed  the  sole  obstruction  to 
a  bodily  collision  with  the  assailed.  In  addition  to  these  means 
the  Ik-  some  cases,  resorted  to  tl  lofty  wooden 

towers,  which  were  covered  by  raw  hides  to  protect  them  from 
tire,  from  within  which  an  in  shower  of  arrows  and  other 

missiles  was  directed  against  the  assailed.  These  ponderous 
engines  were  gradually  moved  toward  the  walls,  on  inclined 
phu  i   with  incredible  toil,  to  give  th 

Bailants  a  commanding  position,  and  to  enable  them,  when  the 
tower  was  brought  sufficiently  near  to  the  wall,  to  he, 
drawbridge  from  it.  to  bridge  the  chasm,  and  bring  on  a  hand- 
to-hand  contest  with  tin'  assailed. 

methods  of  attack  led  to  new  modificatio 
the  def  nee,  which  «  urrounding  the  place  by  wide 

of  which  the  walls  formed  theacarp — the 


216  M  M.MAKY    OF   THE    PEOGEK86    OF    FOBTTFICATIOH. 

counterscarp  being  either  of  earth  6r  revetted  with  stone, 
placed  a  formidable  obstacle  to  the  mode  of  attack  by 
mining,  as  well  as  to  the  ase  of  earthen  mounds,  as  these  Last 
had  i"  be  erected  across  the  ditch  before  sufficicient  proximity 
tn  the  wall  could  lie  gained,  either  to  form  a  communication 
with  its  top,  or  to  plant  the  battering  ram — a  heavy  beam, 
with  an  iron  or  brass  bead,  which,  swung  horizontally  within 
a  wooden  tower,  could  he  driven  by  men  with  sufficient  fo 
to  breach  the  heaviest  walls.  The  ditches,  also,  were  tilled 
with  water  whenever  this  obstruction  could  he  procured. 
When  dry,  they  formed  a  defile  through  which  the  assailed 
often  sallied  upon  the  assailant  with  Buceess. 

664.. .The  gigantic  proportions  often  given  to  the  fortifica- 
tions of  antiquity,  as  well  as  their  extent,  seem  almost  iucredi- 
ble  in  the  present  day.  In  many  cases  a  double  wall  of  Btone 
or  brick  was  rilled  in  between  with  earth,  forming  a  wide  rang 
pail  upon  which  several  vehicles  could  go  ahreast.  !Not  only 
was  the  space  enclosed  within  the  walla  sufficient  for  the  habi- 
tations, but  ground  enough  was  -aid  to  he  taken  in.  also,  for 
agriculture,  so  as  to  add  considerably  to  the  food  of  the  in- 
habitants  and  cattle,  for  the  long  periods  to  which  hlockades 

were  in  many  cases  extended,  when    the   besiegers   had    failed 
in  all  other  means  of  reducing  the  place. 

6651. .The  wall  built  by  the  Romans  in  Britain,  between  Car* 
lisle  and  Newcastle,  to  restrain  the  inclusions  of  the  Pictfl  into 
the  southern  portions  of  the  island,  was  sixteen  miles  in  ex- 
tent, about  twelve  feet  in  height,  and  nine  feet  in  thickn 
The  extent  and  dimensions  of  this  work  sink  almost  into 
insignificance  when  compared  with  those  of  the  celebrated 
wall  of  China,  built  to  restrain  the  incursions  of  the  Tartars. 
This  structure  is  about  1,500  English  miles  in  length,  has  a 
height  of  27  feet,  it.-,  thickness  at  top  being  11  feet.  The  lower 
portion  of  it  is  built  of  dressed  stone,  the  upper  of  well  hurned 
brick.  It  is  flanked  at  distances  of  about  80  yards  apart  by 
towers,  in  which  iron  cannon  are  found.  In  the' great  extent 
it  embraces,  it  necessarily  crosses  hills  and  valleys,  and  in 


SI'MMAKY    OF   TIIK    PROGRESS    OF    FORTIFICATION.  '2 1  7 

many  places  important  defiles.  An  examination  of  its  parts 
has  shown  that  in  its  plan  there  was  an  evident  design  to 
adapt  it  to  those  features  of  its  site,  as  it  is  well  thrown  hack 
to  the  rear  <>t'  difficult  passes ;  and,  at  points  where  there  is 
most  danger  to  be  apprehended  from  invasion,  there  are  sev- 
eral walls  in  succession. 

666../The  mode  of  attack  of  fortified  places  resorted  to  by 
the  ancient.-,  was  reduced  to  settled  rules  and  brought  to  the 
highest  state  of  perfection  by  the  Greeks,  about  the  epoch  of 
xander  the  Great,  and  the  immediate  successors  to  his  vast 
conquests.  An  essential  feature  in  it,  whether  in  the  Bieg<  a  of 
inland  fortresses  or  of  those  on  the  seaboard,  was  to  cutoff  all 
communication  between  the  place  and  the  exterior,  by  hem- 
ming it  in  bysea  and  land  ;  with  stationary  forces, covered  them- 
selves, by  lines  of  intrenchments  strengthened  by  towers,  and, 
iii  tl  isl  place,-,   also  by  fleets.     The  1 

were  thus  prepared  to  repel  all  assaults,  both  from  without  and 

from  the  invested  place.    Having  selected  the  portions  of  the 

place  on  which  the  main  attack  was  to  be  directed,  a  second 
line  was  formed  parallel  to  the  first,  which  was  covered,  and 
constructed  of  timber  and  wicker  work,  and  secured  with  raw 
hide-  to  prevent  its  being  set  on  fire.  From  this  sheltered  po- 
sition, which  Berved  also  the  purposes  of  a  lodging  for  the  be- 
i  rs,  the  were  annoyed  with  missiles  thrown  from 

all  the  artillery  known  in  that  day.  consisting  of  the  ordinary 
bow.  the  cross-bow,   and    the   varioii-   machines  for   projecting 

heavy  stones  and  other  projectiles.  Under  the  diversion  thus 
made,  the  1"  pushed  forward  from  this  line  several  COY' 

ered  approaches  directly  upon   the  place,  for  the  put 
gaining  the  count*  recarp,  and  from  that  position  filling  tip  the 
ditch  with  Btones,  earth,  heavy  bags,  etc.,  bo  prepare  the  way 
for  placing  the  battering-ram  in  position  to  breach  the  wall. 
The  tower  in  which  this  machine  wn>  placed  usually  e 

by  troops,  who  cleared 
the  top   of  the  wall  of  the  b 

quently   aided  b  high  towers,  which  ced 

28   . 


218  MMMAin     01    THE    FBOGR1  RTIFICAT10H, 

either  on  the  natural  level  of  the  ground,  or  upon  artificial 
mounds,  forming  inclined  planes,  bo  that  any  desirable  com- 
mand over  the  interior  could  be  obtained* 

667...The  defence  was  mostly  of  a  passive  character:  the 
besieged  trusting  maialy  to  the  strength  of  their  defer 
kinder  cover  of  which'they  resorted  to  all  the  means  used  by 
the  Besiegers,  for  attaining  the  latter  when  they  came  within 
reach  o\  their  missiles ;  nsing,  tor  the  near  defence,  cranes  and 
other  devices  to  seize  upon  the  implements  planted  at  the  foot 
of  the  wall  ;  and  constructing  galleries  of  countermines  to 
overwhelm  the  artificial  monnda  and  their  towers, 

668... The  Romans  evinced  their  decided  military  aptitude, 
not  only  in  the  employment  of  the  ordinary  systematic  meth- 
ods of  the  attack  and  defence  of  fortified  places,  but  in  their 
application  of  the  cardinal  principle  of  mutual  defensive  rela- 
tions between  the  parts  of  a  fortified  position,  obtained  by 
advanced  and  retired  portions  of  the  enceinte;  and  also  in 
the  adaptation  of  intrenchments  to  the  natural  features  of  the 
site,  as  shown  in  the  fortifications  of  some  of  the  permanent 
frontier  camps  of  their  military  colonies.  The  application  of 
these  principles  ha\  e  also  been  noticed  in  some  of  the  fortified 
positions  of  India,  which  consisl  of  a  mural  enceinte  with 
earthen  ramparts,  Hanked  by  round  tower.-,  and  of  round  tow- 
er.- in  advance  of  the  enceinte  and  connected  with  it  by  capon- 
nieres. 

669...  With  the  decadence    of  the    Roman    empire,  the  art  of 

fortification,  like  the  other  branches  of  the  military  art,  was 
brought  to  so  low  a  stage  that   Btrongholds  which,  defended 

with  skill  and  energy,  would  have  baffled  the  eil'orts  of  a  well- 
trained  assailanl  in  the  art  of  attack,  fell,  almost  without  re- 
sistance, into  the  possession  of  the  fierce  Northern  hordes  by 
which  the  whole  of  civilized  Europe  was  overrun.  The  re- 
mains of  the  structures  raised  for  defensive  purpose.-,  during 
the  prosperous  days  of  the  empire,  were  probably  the  sole 
means  of  protection  afforded  to  the  inhabitants  of  the  towns  that 
still  maintained  a  nucleus  of  population,  until  the  rise  of  the 


H 


SUMMARY   OF   THE    PROGRESS   OF   FORTIFICATION".  219 

Western  empire  under  Charlemagne;  and  it  was  the  necessity 
fell  by  this  conqueror,  not  only  of  securing  his  conquests,  btit 
of  checking  the  irruptions  of  the  barbarous  tribes  along  his 
extended  frontier,  which  Led  him  to  erect  t&tes  <l<  pant  on  the 
frontier  rivers,  and  a  line  of  strong  to.wers,  for  garriaona  of  a 
few  men,  upon  the  most  inaccessible  ami  prominent  points  of 
this  frontier;  the  latter  being  a  means  which  was  subsequently 
r  a  like  purpose  in  the  Spanish  peninsula.  Henry 
I.,  bf  Germany,  introduced  a  more  important  and  more  syste- 
matic a<l<liti<>n  to  these  permanenl  frontier  defences,  by  sur- 
rounding the  frontier  towns  and  villages,  occupied  by  military 
Colonists,  with  walls  and  ditches,  to  secure  them  from  such  at- 
tacks us  they  might  be  exposed  to.  and.  subsequently,  by  add- 
ing  a  second  line  of  strongholds  within  the  frontier,  by  which 
an  irruption1  through  the  frontier  line  mi^ht  still  he  checked. 
07O...During  the  general  disorganization  of  states  under  the 
feudal  system,  the  {\-r<-  cities,  which  depended  for  their  de- 
fence .,n  the  burghers  composing  the  different  crafts,  every 
individual  who  could  maintain  a  t'ew  retainers  in  his  pay,  ami 
the  clergy  even  resorted  to  such  means  of  defence  as  would 
re  them  from  the  attacks  of  Others  in  a  like  condition, 
or- which  would  enable  them  to  carry  out  that  s}rstem  of  pill  a 
that  had  beco  eral  amongst  the  nobles  and  other  military 

chief  tail 

!...l'"roin    this    state    of    society    wrung    Up    tie 

placed  in  the  most  inaccessible  positiooa  on  the  lines  of  com- 
munication which  the  little  inland  commerce  that  was  still 
carried  on  was  obliged  to  tra  I 

vided  with  every  possible  device  for  an  obstinate  passive  de- 
ing  surrounded  by  a  wide   and   deep  ditch,  or  moat, 

•which  a  drau-ln  the  only  communication  t.<  the 

main   entrance,  which,  il  on   the 

rior  and  closed  w  ith  n  doors;  the   tortuo 

which  led  from    tie     I 
furtk 
at  a  moi  the 


MMMAHV    OF    mi.    PKOGBE8E    OF    FOB  1  OTI0ATTON. 

ordinary  measures  of  loop-holes  and  machicoulis  in  the  walls 
and  tower.-  for  annoying  tin'  assailant,  a  high  interior  tower, 
termed  a  keep,  or  donjon,  was  often  added,  which,  command- 
ing the  exterior  defences,  served  also  as  a  watch-tower  over 
the  adjacent  country. 

672. ..'Hie  keep,  being  the  last  defensible  point,  was  in  some 
cases  provided  with  a  secret  subterranean  passage,  having  its 
putlet  in  a  distant  concealed  spot,  through  which  .succor  could 
be  introduced  into  the  beleaguered  castle,  and,  in  the  last  ex- 
tremity, the  garrison  find  safety  in  a  stealthy  flight. 

673. ..The  fortifications  of  towns  partook  of  the  same  charac- 
teristics as  those  of  castles.  From  the  custom  of  assigning  to 
the  different  burgher  crafts,  each  of  which  had  an  independent 
military  organization,  the  exclusive  guardianship  of  portions  oij 
the  enceinte,  as  well  as  their  erection  and  repairs,  great  diver- 
sity, and,  frequently,  a  whimsicality,  in  the  defensive  arrange- 
ments, was  the  natural  result;  the  evidence  of  which  still  ex- 
ists in  the  remains  of  the  walls  of  some  of  the  old  continental 
cities.  The  art,  for  the  most  part,  was  practiced  by  ambula- 
tory engineers,  who,  like  the  secret  orders  by  whom  the  bridges 
and  churches  of  the  same  period  were  built,  ottered  their  ser- 
vices wherever  they  were  wanted.  Many  new  ideas  were  also 
introduced  from  the  East  by  the  Crusaders,  as  exhibited  in  the 
fortifications  of  castles  and  cities  belonging  to  the  templars 
and  other  religious  military  orders. 

674.. .With  the  invention  of  gunpowder  and  its  application 
to  military  purposes,  a  gradual  revolution  took  place  in  the 
general  forms  and  details  of  fortification.  It  was  soon  seen 
that  naked  walls  alone  did  not  afford  space  enough  for  the  new- 
military  machines,  nor  sufficient  protection  against  the  projec- 
tiles thrown  from  them.  This  led  to  the  introduction  of  earthen 
ramparts  and  parapets,  which  were  placed  against  the  walls 
and  suitably  arranged  to  meet  the  exigencies  arising  from  this 
change.  The  art  began  to  receive  something  like  a  scientific 
basis  about  this  time  in  Italy,  from  which  the  names  and  forms 
of  most  of  thi'  elements  of  fortification  now  in  use  are  derived. 


SUMMARY   OF   THE    PROGRESS   OF    l'<  >K'i  !!■  T«   \TION.  221 

The  Italian  engineers,  like  their  predecessors,  went  from  state 
to  state  t<»  offer  their  services  wherever  they  were  needed,  and, 
in  tli is  way,  disseminated  the  principles  of  their  scl 1  through- 
out Europe.  It  was  at.  this  epoch  that  the  bastioned  form  of 
fortification  first  appeared,  hut  the  precise  date  and  the  author 
of  the  invention  are  both  unknown.  With  its  introduction, 
the  importance  of  separating  the  parts  of  a  line  of  fortification 
into  advanced  and  retired  parts%the  hitter  flanking  and  defend- 
ing the  former,  seems  to  have  been  recognized  as  an  essential 
principle  of  the  art.  With  these  changes  in  the  form  of  the 
enceinte  the  art  was  gradually  improved,  by  the  addition  of 
outworks  to  increase  the  amount  of  cross  and  flank  fire  ;  the 
introduction  of  bomb-proof  shelters  for  the  troops  and  other 
purposes;  the  substitution  of  earthen  for  stone  parapets;  and 
the  attempt  to  conceal  the  scarp  walls  from  the  enemy's  bat- 
teries, by  decreasing  the  command  and  deepening  the  ditches 

of  the  enceinte. 

675...By  these  gradual  changes,  stone  walls,  which  in  the 
old  fortifications  were  the  essential  defensive  feature-,  came 
at  length  to  l.e  regarded  in  their  true  character, Bi'mply  as  pas- 
sive obstacles  to  an  open  assault  by  escalade.  The  property 
of  earthen  parapets  of  resisting,  without  material  loss  of 
strength,  the  long  continued  fire  of  the  assailant's  lea- 
guns,  showed  that  the  same  defensive  means  were  applicable 
both  to  works  of  a  permanent  and  of  a  temporary  character, 
and  were  equally  available  for  the  purposes  of  the  assailant 
and  the  assailed.  The  measures  for  the  attack  and  for- the  de- 
fence of  positions  were  thus  reduced  to  the  sa general  prin- 
ciples, differing  only  in  the  forms  and  dimensions  of  the  ■ 
mentary  parts,  ;i-  circumstam              led  to  demand. 

676...Italia2*  School.     A>  above  stated,  the  first  employ- 
ment of  hasl  ist,  was  made  by  the   Italian 
far   ;i-   ha  ined,  toward  the 
the  fifteenth,  or  the  commencement   of  tl  enth 
tury.     To    whom   the    credit    of  their    invention    is  due, 
not  known.     In  the  earlier  fronts  of  the  ]•               bool  the  I 


222  SUMMARY    OF  THE    PROGRESS    OF    FORTIFTOATION. 

tions  ire  very  small,  and  they  are  connected  by  curtains  vary- 
ing frotn  250  to  500  yards  in  length.  The  bastion  flanks, 
which  were  usually  perpendicular  to  the  curtains,  were  divided 
into  two  portions ;  that  aext  to  the  curtain,  which  was  one- 
third  of  the  entire  Hank,  was  thrown  back,  and  covered  by  the 
portion  in  advance;  the  advanced  portion,  thus  formed,  re- 
ceived the  name  of  the  orillon.  The  lower  part  of  the  retired 
portion  was  casehiated  for  cannon  ;  and  behind  this,  and  sepa- 
rated from  it  by  a  dry  ditch,  ruse  a  second  think,  having  the 
same  command  as  the  other  parts  of  tin-  enceinte  parapet. 
In  .-.mie  cases,  a  small  and  very  obtuse  bastion  was  erected  at 
the  middle  of  long  curtains.  The  ditches  of  the  enceinte 
were  usually  about  100  feet  wide,  and  l'4  feet  deep,  the  coun- 
terscarps being  parallel  to  the  bastion  faces.  A  scarp  gallery, 
for  the  purpose  of  mining,  ran  throughout  the  enceinte  scarp, 
and  communicated  with  galleries  leading  to  other  points.  The 
parapets,  at  first  of  masonry,  were  afterward  of  earth,  and 
made  from  IS  to  2-i  feet  thick.  The  earth  of  the  rampart  was 
sustained  on  the  interior  by  a  wall.  Ramps  established  a 
Communication  between  the  interior  and  the  rampart. 

677.. .The  defects  of  these  early  fronts  were  soon  felt,  and 
a  more  complicated  hut  improved  trace  adopted,  in  which  the 
bastions  were  enlarged,  and  the  curtains  diminished.  The  re- 
tired thinks  were  still  retained,  but  the  orillon,  instead  of  being 
angular,  was  rounded.  To  these  improvements  cavaliers  were 
sometimes  added  to  the  bastions,  which,  in  those  cases,  were 
made  without  retired  thinks,  or  they  were  placed  on  the  cur- 
tains, when,  from  the  configuration  of  the  site,  some  portion 
of  the  ground  within  cannon  range  could  not  he  swept  from 
the  enceinte;  parapet.  The  covered-way  was  introduced,  and 
became  an  integral  part  of  the  front;  and  a  small  demilune 
or  ravelin  was  placed  in  advance  of  the  enceinte  ditch,  form- 
ing a  tete  de  pont  to  cover  the  communication,  at  the  middle 
of  the  curtain  across  the  main  ditch,  between  the  enceinte  and 
the  exterior.  The  covered-way,  which  at  first  was  of  uniform 
width,  and  bordered  the  main  and  demilune  ditches,  was  snh- 


8UMMAKY   OF   THE    PBOGEE88    01    FOBTIFIOATKHSF.  228 

sequently  provided  with  salient  and  reentering  places  of  arms. 
These  various  essential  parts  of  a  fortified  froni  were  gradually 
ameliorated  by  the  Italian  engineers,  bu!  not  before  the  Ita- 
lian school  had  left  its  impress  upon  the  fortification  of  all  the 
Other  states  of  Europe,  as  the  Italian  engineers,  from  their  su- 
perior acquirement.-,  were  in  demand  throughout  these,  states. 

678.. .Spanish  School.  This  school,  as  seen  in  the  existing 
fortifications  of  Spain,  shows  the  influence  of  the  Italian 
school,  though  modified  by  national  characteristics.  These 
are  observed  in  the  greater  dimensions  given  to  their  profiles, 
an  augmentation  of  the.  means  of  annoying  the  besiegers  by 
artillery  and  musketry,  the  construction  of  complex  interior 
retrenchments,  and,  frequently,  the  omission  of  a  coven-d-wav  : 
the  entire  organization  of  the  works  pointing  toward  an  ob- 
stinate passive  defence,  rather  than  to  one  in  which  sorties 
may  play  an  essential  part — a  mode  of  defence  in  which  the 
Spaniards,  at  all  periods  of  their  history,  have  exhibited  con- 
summate skill  and  perseverance. 

From  the  broken  character  of  many  of  the  sites  of  their  for- 
tifications, the  Spanish  engineers  have  resorted  to  detached 
Works  to  occupy  commanding  positions  in  advance  of  the  main 
work.  These  detached  works  are  also  organized  for  a  purely 
passive  defence;  being  left  to  their  own  resources  rather  than 
iy  BUpport  from  the  main  work. 

< *►  7 1 ♦ . . . I  > •  i <  u  School.  This  Bchool  took  its  rise  in  the  politi- 
cal qec<  of  the  tinn.-.  in  which  the  national  spirit  was 
aroused  to  throw  off  an  onerous  foreign  yoke  The  aquatic 
character  of  Holland,  and  the  want  of  time 'and  pecuniary 
meat  lients  of  defence  which  are  n< 
wanting  under  like  circumstances.  Tie  deficiency  of  eartlj 
led  to  the  formation  of  low  parapets  for  the  main  enceinte,  ami 
wide  ditches  filled  with  water.     The  main  enceinte  was  usually 

'■oiid  one  with  a  very   low   parapet,  t 
the  surfacM   of  the  wet   ditch;  and   this   Becond    enceinte 

arated  from  the  fii  dry   ditch,  which  favored  Borl 

and  which  v.  ded  with  all  the  I  -  palisad*    . 


L'L'l  si  MMAKV    OF   THE    PBOORE8S    OF    FORTIFICATION. 

hours  and   block-houses,  for  offensive  returns  and   surpri 
The  second  enceinte  was  covered  by  a  glacis  in  advance  of  the 
main  ditch.     The  covered-way  left  between  the  glacis  and  the 
ditches  was,  to  a  great  extent,  frequently  deprived  of  its 

ial  offensive  feature,  by  the  introduction  of  an  exterior 
wel  ditch,  placed  at  the  foot  of  the  glacis  and  enclosing  it  j 
over  winch  communication  with  the  exterior  was  kept  open  by 
temporary  bridges.  The  work.-  were  usually  greatly  multi- 
plied and  their  combination  complicated.  The  whole  of  the 
defensive  measures  of  this  school  seem  to  have  had  for  their 
object  a  strictly  passive  resistance.  With  this  view,  long  ii 
of  entrenchments,  supported,  from  distance  to  distance,  by 
tort.-,  connected  their  frontier  towns  and  villages,  affording 
Miilicient  obstacle  to  marauding  expeditions,  by  requiring  the 
efforts  of  a  strong  force  to  break  through  them.  At  a  later 
period,  taught  by  the  experience  of  their  earlier  efforts  against 
the  most  military  state  of  that  epoch,  covers  thai  would  afford 

iirity  against  incendiary  modes  of  attack  were  provided; 
and  reveteraents  of  masonry  substituted  for  the  earthen  slopes 
of  the  ramparts,  particularly  where  the  ditches  were  dry. 
These  successive  changes,  partly  induced  by  the  Italian  and 
Spanish  schools,  with  whose  methods  the  hutch  engineers  he- 
came  acquainted  through  their  connection  with  Spain,  were 
the  natural  precursors  of  the  methods  of  Coehorn,  the  most 
distinguished  engineer  ot  the  Dutch  school,  whose  works  are 
characterized  by  many  of  its  essential  features. 

680... < ii-:i:.M an  School.  The  Germans  reckon  a  number  of 
original  writers  on  fortification,  among  the  most  noted  of  whom 
are  the  celebrated  painter  Albert  Durer,  Daniel  Speckles,  and 
Kimpler.  In  the  propositions  of  these  writers  are  to  be  found 
the  influence  which  the  Italian  school  naturally  exercised 
throughout  civilized  Europe,  and  the  germs  of  many  of  the 
view.- held  by  the  German  school  of  the  present  day,  which 
last  seem,  however,  to  have  been  taken  more  immediately 
from  the  propositions  of  Montalembert  and  Carnot. 

681. ..Swedish  School.    The  part  played   by  Sweden  upon 


summary   OF  Tin:   PROGRESS  Of   FORTIFICATION.  225 

the  theatre  of  Europe,  under  her  two  celebrated  monarchs, 

Gustavus  Adolphus  and  Charles  X  II..  served  to  de\  el,.],  in  this 
nation  every  branch  of  the  military  art.  A  number  of  dis- 
tinguished generals  and  engineers  arose  under  these  monarchs, 
who  combined,  with  the  practice  of  their  profession,  a  study 
of  its  theory.  Among  the  engineers  of  this  school  Virgin 
holds  the  first  place.  The  climate  and  the  nautical  habits  of 
a  large  portion  of  the  Inhabitants  seem  to  have  led  to  the  con- 
struction of  land  defences  analogous  to  those  of  ships;  as 
shown  in  the  use  of  casemated  batteries  in  several  tiers,  both 
for  sea-coasi  and  inland  fortifications.  In  this  school  the  bas- 
tioned  system  seems  to  have  been  generally  adopted  for  the 
enceinte,  great  attention  being  paid  to  covering  the  faces  of 
the  works  from  enfilading  fire,  to  providing  casemates  having 
reverse  views  on  the  besieger's  works,  and  particularly  in  so 
arranging  the  interior  defences  that  each  part  should  not  only 
contribute  to  the  support  of  the  others,  but  be  capable  of  an 
independent  resistance.  These  dispositions  necessarily  led  to 
at  complication  and  multiplicity  of  works,  as  shown  in 
the  writings  of  Virgin. 
682...Fbbn<  u  School!  What  may  be  termed  the  character' 
this  seho.,1  are  to  be  seen  rather  in  the  method  of 
Cormontaingne,   and    the    teachings    of    the    two  celebrated 

Schools,    Mi  zieres    arid    "Met/,  for    the    education    of  eiiL.Mii' 
than  in  the  practice  of   Yauhan.  although  his  authority  ha- 

<d  a  preponderating  influence  throughout  Europe;  and  is 
still  appealed  to.  in  all  great  problems  of  the  art,  by  i  i 
in  polemical  disput<  s.     Tic  In  neb  have  evinced  in  tl 
all  the  other  arts,  that  spirit  of  systematic  combination  wl 
form  '   their  most  striking  national  trait-.      \\   I 

eluding   an    active   defence,  the   most  noted  authors  of   I 

•ased  their  methods  more  upon  R  ootnbinatiou  of 
elements  by  which   the  can   he  c 

by  stop,  by  the  lire  of  |  -  than   h  Until 

within  the   last    thirty  or   fort; 

peri  .  and 

28 


226  PROGRESS    "I     THE    ATTACK 

a  subjection  t<>  mere  authority.  This  accusation,  hdwever, 
true  rather  of  the  polemical  writings  of  the  day,  growing  out 
of  the  propositions  of  Montalemb<  rt,  than  of  the  practice  of 
the  French  engineers;  and  it  was,  iu  a  measure,  strengthened 
by  a  miscohception  on  the  part  of  foreign  engineers,  of  the 
real  purposes  of  the  instruction  given  in  their  schools  of  pro- 
nonal  training.  Still,  recognizing  in  Yanhan  and  Cormon- 
taingne  tin-  chief  founders  and  authorities  of  their  school,  the 
French  engineers  of  the  presenl  day  discard  no  defensive  ele- 
ment that  has  stood  the  test  of  experience,  or  is  consonant 
with  Bound  professional  views.  Basing  their  art  npon  incon- 
brovertable  principles,  its  practice  is  made  by  them  t<.  conform 
to  the  exigencies  of  each  case  a--  presented  by  it>  own  data. 


PROGRESS   OF    THE    ATTACK   SIXCE   THE 
INVENTION   OF   FIREARMS. 


683..  .Tin'  introduction  of  cannon,  although  it  led  to  important 
changes  in  the  measures  bojh  of  the  Attack  and  defence,  still 
did  not,  for  a  considerable  period,  bring  about  any  very  decie 
results  in  the  length  of  sieges.  The  means  which  it  afforded 
the  defence  of  reaching  the  *  besiegers  at  a  distance,  and  de- 
stroying all  the  methods  of  approaching  and  annoying  the 
place  which  had  been  hitherto  used,  led  to  the  substitution  of 
the  ordinary  trenches  of  the  presenl  day  lor  the  wooden  gal- 
leries and  other  similar  expedients  tor  approaching  under 
cover ;  and  to  the  erection  of  batteries  at  distant  points  to  open 
1. reaches  in  the  walls.  Lines  of  circuinvallation  and  counter- 
vallation,  which  formed  so  prominent  a  feature  previously  to 
this  epoch,  was   the  only  one  which  still  kept  its  place,  as  it 


SINCE    ill i ;    iwiaiio.n    <U'    nKRARMB.  2'_'7 

has  done  to  a  greater  or  Less  extent  to  the  present  day.  For 
the  purpose  of  effecting  at)  entrance  into  the  place,  breaching 
batteries  were  erected  opposite  the  points  deemed  most  favora- 
ble. They  were  placed  either  on  natural  elevations  <>f  the 
ground  or  upon  artificial  mounds,  with  the  object  of  attaining 
the  wall  to  be  opened  near  its  foot  and  thus  form  a  breach  <>f 
easy  ascent.  These  batteries  were  enclosed  in  works  of  suffi- 
cient size  and  strength  to  hold  garrisons  to  secure  them  from 
sorties.  The  approaches  were  made  as  at  present  1>\  zig-2 
along  the  capitals  of  the  salients,  to  the  counterscarp,  where 
a  covered  descent  was  made  into  the  ditch,  opposite  the  breach, 
preparatory  to  its  assault.  When  the  wall  was  not  exposed  to 
a  distant  fire,  the  besiegers  were"  obliged  to  carry  the  covered- 
way  by  assault  and  establish  their  breaching  batteries  on  the 
at  of  the  £  In  carrying  forward  these  works,  the  he- 

were  subjected  to  great  losses  and  delays,  owing  to  the, 
magnitude  and  multiplicity  of  the  works  they  were  obliged  to 
complete  :  to  the  imperfect  character  of  their  artillery  and  the 
faulty  position  of  their  batteries,  by  which  they  were  unable 
(0  keep  under  the  fire  of  the  place;  the  want  of  connection 
between  the  separate  approaches;  and  the  exposure  <>t'  the 
wi nk men  in  the  trenches  to  sorties,  the  troops  for  their  support 

in  the  enclosed  works  in   the   rear  being  t listant   to  . 

timely  succor ;  besid  enclosed  works  naturally 

became  the  chi<  f  objecfta  for  the  lire  <>t'  the  besieged,  the 
glomeration  of  troops  in  them  added  materially  to  the  1- 
Owing  to  these  imperfections  in  then 

sure.-  of  attack,  the  lie   to    make    a 

and  prolonged  d<  :•  became  the  m<.>t    in 

military  operations    of   this  period,  in  which  captains  of  the 
brity  sought  for  opportunities  of  distinctio 
-  I...i!ut    littli  made    in    the    D  just 

ribed,   until    Yauhan     appeared    upon    the    - 
:-lv  to  him,  Montluc,  a  distinguished   French  and 

ad  introduced  short  brai 
which  were  run  out  from  tin 


228  pro  mi    aii  \<  k 

few  troops  for  the  immediate  protection  of  the  workmen,  but 
these  were  found  to  be  very  insufficient  in  repelling  sorties  of 
any  strength.  The  event  which  seems  to  have  had  the  great- 
on  the  subsequent  progress  of  both  the  attack 
and  defence  was  the  memorable  siege  of  Candia,  in  which 
volunteers  from  all  parts  of  Europe  were  engaged,  who,  after 
its  close,  disseminated  throughout  their  respective  count] 
the  results  of  the  exp<  rience  they  had  there  acquired. 
Whether  the  idea  of  the  parallels,  now  in  use  in  the  attack, 
originated  there,  <<r  with  Vauban,  this  eminent  man  was  the 
first  i<>  establish  them  in  a  systematic  manner,  and  to  demon- 
strate 1>\  experience  their  controlling  importance  in  repressing 
sorties.  The  introduction  of  this  important  element  in  the 
attack;  the  concentration  of  the  fire  of  batteries,  by  giving 
them  enfilading  positions;  the  invention  of  the  ricochet,  as  the 
most  powerful  destructive  means  against  the  defences;  the 
avoidance  oi  open  assaults,  which,  even  when  successful,  arc 
made  at  a  great  sacrifice  of  life,  preferring  to  them  the  Leu 
brilliant  but  slower  method  of  skill  and  industry,  by  which 
the  Mood  of  the  soldier  is  Bpared,  and  the  end  more  surely 
attained,  such  are  the  important  service-  which  the  attack 
owes  to  Vauban;  which  has  given  it  its  present  marked 
superiority  over  the  means  of  defence;  and  to  which  the 
oce  and  experience  of  engineers  since  his  day  have  added 
nothing  of  marked  importance. 

685... Com  ii  H'>.\.  Whil.-t  the  attack  has  thus  been  brought 
to  such  a  Btate  of  perfection,  and  its  destructive  means  arc 
still  on  the  increase, from  the  rapid  improvement  daily  making 
in  the  range  and  certainty  of  aim  of  cannon,  as  well  as  in  the 
ease  with  which  the  mosl  gigantic  armaments  can  be  now 
transported  to  distanl  points,  both  on  sea  and  land,  the  means 
of  deft  nee.  bo  far  as  relates  i"  fortification  alone,  are  hut  little,  if 
at  all,  in  advance  of  what  they  were  in  the  time  of  Yauham 
Upon  the  chief  defects  and  wants  of  the  art,  there  exi.-ts  hut 
slighl  divergence  of  opinion  among  engineers  generally;  not 
so  with  respect  to  the   remedy;  opposite  opinions  being fre- 


SINCE  THE    QJVENTIOH    OF    IIEEARM8.  229 

quently  drawn  from  the  same  class  of  facts,  and  the  same 
authority  frequently  cited  to  sustain  opposite,  views.  Whilst 
eacli  new  dispntant  denounces  systematizing  and  rl  1  ■  ■  systems 

of  Others,  his  remedy  for  tlie  abuse  complained  of  is  n.-ually  :i 
Bystem  of  his  own,  which  not  unfrequently  oners  but  the 
disjecta  ?nembra  of  those  of  others.  The  Bum  of  the  whole 
matter  is,  that  fortification  is  an  art  the  component  elements 
and  principles  of  which  are  tew  and  simple.  It.-  efficiency 
Consists  neither  in  short  lines  of  defence  nor  long  lines  of  de- 
fence; nor  in  large  or  small  bastions;  nor  in  the  adoption  of 
this  or  that  system;  but  in  the  judicious  adaptation  of  these 
principles  and  element.-  to  the  locality  to  he  defended,  and 

the  purposes  of  the  defence.       Til  this    resided  the  excellence  of 

the  engineer's  art.  lie  who  should  combine  his  element?-  in 
the  arrangement  of  a  small  work,  with  a  Weak  garrison,  as  in 
one  intended  for  the  occupation  of  an  extensive  position  by  a 
large  force,  or  should  blindly  adopt  the  same  method.-,  for  an 
iiregnlar  site  that  he  would  for  a  horizontal  one,  whatever  his 
acquisitions  or  pretensions  may  lie,  has  but  a  small  claim  on 
the  title  of  military  engineer. 

686~.From  the  preceding  brief  summary,  it  will  he  seen 
that  the  art  of  fortification,  in  it-  progress,  has  kept  pace  with 
the  measures  of  the  attack ;  ••  bavingh 

brought  about  by  changes  either  in  the  arms  used   by  the 
lant,  or  by  the  introduction  of  some  new  mode  of  assault. 
The  same  cauw  -       isl  continue  to  produce  the  same  eflR 
At  no  past  period  has  mechanical  invention,  in  it-  bearing  on 
the    military  art.  been   m<  re  than    at    the  present  day. 

The   improvement   that   ;  made  in   the  r.r 

and  accuracy  of  aim  of   both  small  arms   and  cannon,  the  par- 
tial adoption  of  wrou^ht-iron  and   steel  for  floating  : 
and  men!  of 

important  epoch   in   the  irt.     Tie 

cannon  will  the  aasa 

in  the  selection  of  pxj  iud  will   thus  in- 

crease the  diflicultiee  in  adapl  s  to 


230  PROGRESS  OF  THE  ATTACK. 

the  site,  and  in  giving  adequate  Bhelter  to  the  garrison  and 
armament.  Whilst  the  defence  will  be  to  this  extent  weak- 
ened, the  approaches  of  the  r  will  be  rendered  more 

]m  rile us  and  more  difficult,  from  the  greater  range  and  accu- 
racy of  small  arms.  The  greal  destruction  of  life,  in  open 
alts,  by  columns  exposed  within  so  long  a  range,  must 
an  additional  value  to  intrenched  fields  of  battle;  and  we 
may  again  see  fieldworks  play  the  part  they  did  in  the  defence 
of  Sebastopol;  and  positions  so  chosen  and  fortified  that  not 
only  will  the  assailant  be  forced  to  intrench  himself  to  assail 
them,  but  will  find  the  varying  phases  of  his  attack  met  by 
corresponding  changes  in  the  defensive  dispositions. 

687. ..The  engineers  of  our  own  country,  without  servilely 
copying  any  of  the  Bystemi  in  vogue  in  Europe,  have,  in  most 
of  their  enclosed  works  of  any  Bize,  adopted  the  bastioned  sys- 
tem. As  the  works  erected  by  them  are  chiefly  for  sea-coast 
defence,  their  water  fronts  usually  consist  of  one  or  more  tiers 
of  casemates  surmounted  by  a  barbette  battery;  whilst  the 
land  fronts  present  a  rampart  arranged  for  open  defences.  In 
small  works,  where  the  properties  of  the  bastioned  Bystem 
could  not  be  developed,  owing  to  the  limited  Bize  of  the  fronts, 
flanking  dispositions  have  been  made,  either  by  casemated 
capohnieres  or  by  counterscarp  galleries;  and.  in  cases  wh 
a  Large  amount  of  fire  was  requisite  to  sweep  a  given  ap- 
proach by  sea,  they  have  resorted  to  the  castellated  form  oi 

casemated    batteries;    combining    several     tiers   of   casemates 

with  a  barbette  battery  on  tdp. 

Whilst  thus  adhering  to  well  settled  principles  and  the  prac- 
tice of  the  besi  European  authorities,  our  engineers  have  con- 
tributed their  share  to  the  improvement  of  the  details  of  the 
art.  The  works  erected  by  them,  within  the  last  thirty  or 
forty  year.-,  are  remarkable  for  the  excellence  of  the  materials 
employed  l»y  them,  the  superior  skill  shown  in  the  workman- 
ship, and  the  care  with  which  every  detail  is  worked  out  to 
subserve  the  object  in  view.  In  these  respects  and  in  the 
general  adaptation  of  the  plan  to  the  site,  it  is  not  claiming 


IXFi.i  I  v  I     OF    li:i:i  <•!  I ,.\i;i  m-   OF   BITE.  231 

too  much  to  Bay  that  the  works  erected  by  them  are  Dpi  Bur- 
passed,  and,  in  sonic  points,  Dot  equalled  by  any  similar 
works  in  Europe. 


RIFIMCE  OF  IRREGULARITIES  OF  SITE  (IX  THE  FORMS 

AMI  G0HM1HH  OF  THE  ELEHEMS  OF 

PER1AXE.VT  WORKS. 


■i  treating  the  subject  of  permanent  fortification,  the 
same  order  is  nsnally  followed  as  in  the  discussion  of  tempo- 
rary fortification,  viz:     1st.   An  exposition  of  the  general  prin- 
ciples with   their  applications  to  a  horizontal  site.     2d.    ' 
various  modifications  of  detail  occasioned  by  irregularities 
ttted  in  nature.     3d.  The  various  accessory  m< 
itrengthening  weak  points,  called  for  by  peculiar  circum- 
of  locality,  which   either  preclude  the  applicatioi 
the  ordinary  means  or  require  others  in  addition  to  them. 

39...Whether  the  -  rfecdy  level  within  the  range  of 

the  fire  of  the  work  «»r  i-  irregular,  tin  d  condil 

arr  to  1"'   satisfied   in   each    case,   in   order  tliat  tin-  work  shall 
have  all  the  efficiency  of  which  it  is  capable.    These  are: 
Thai  or   to  the   <;■  r  which 

enemy   must   approach  them,  or  from  which   he  can    am 
them   by  his  fire,  i   be   brought  ander  the  fire  of 

2cl,  That    ii"    point   of  left 

uanled  l»y  their  own    fin  , 
the  •  porary  shelter  from   fin  .  ma 

tinn 


232  i.mi.uvi    "!'   i i:ki:< .ti.a i:t 1 1 i:s  of  site. 

within  the  defences  shall  be  sheltered  from  the  enemy's  fire 
in  any  position  he  may  take  exterior  to  them. 

690...The  problem  presented  for  solution  to  the  engineer  in 
irregular  sites  is,  frequently,  one  of  no  ordinary  complexity  ; 
demanding  a  minute  and  laborious  Btudy  of  the  natural  fea- 
tures of  the  position  in  their  relations  to  the  defence;  c>n- 
Dected  with  a  tentative  process,  of  which  the  object  is  so  t<> 
modrry  the  plan,  relief  ami  details  ordinarily  adopted,  as  to 
adapt  them  in  the  best  manner  to  the  given  position.  X<» 
rules,  hut  of  a  very  general  character,  can  he  laid  down  for 
the  guidance  of  the  engineer  in  such  cases.  Of  this  class  the 
following  are  the  most  obvious  and  essential,  and,  when  prac- 
ticable, should  he  adhered  to  : 

691. ..1st.  It  has  already  been  observed  that,  from  the  means 
used  in  the  attack  of  permanent  works,  the  more  plunging  the 
fire  of  the  work  the  more  efficacious  will  it  prove  in  retarding 
the  enemy's  progress.  The  efficiency  of  this  fire  will  depend 
upon  two  causes,  the  command  of  the  work  over  the  point  to 
be  attained,  and  the  direction  of  the  ground  with  respect  to 
the  lines  by  which  it  is  swept. 

692.. .As  to  the  command  of  the  work  over  the  exterio? 
ground,  it  has  already  been  shown  that  motives  of  economy 
restrict  it,  in  most  cases,  within  very  narrow  limits,  where  to 
obtain  it  artificial  embankments  have  to  be  employed.  To 
augment,  therefore,  in  the  greatest  degree  this  element  of  the 
defence,  advantage    should  he  taken  of  the  natural    features  of 

the  locality,  by  placing  tin'  principal  lines,  from  which  the  ex- 
terior ground  can  he  seen,  on  the  most  commanding  or  highest 
points  of  the  site.  If,  with  this  position  given  to  the  principal 
lines,  the  ground  swept  falls,  or  slopes  toward  them,  the  most 
favorable  combination  for  an  efficacious  plunging  lire  will  he 
obtaipedj  for,  with  this  direction  of  the  ground,  the  enemy 
will  meet  with  far  greater  difficulty,  to  put  himself  under  shel- 
ter by  his  works,  than  where  the  ground  falls,  or  slopes  from 
the  line  by  which  it  is  swept  ;  as  the  surface,  in  the  latter 
case,   descending   in   the  rear  of  the   cover  thrown  up  by  the 


INFLUENCE   OF   tBBEGl  LABTTIEB   OF   BITE.  233 

enemy,  will  be  screened  to  a  greater  extent  than  in  the*former, 
where  it  rises  in  tlio  rear  of  the  cover. 

693. ..The  general  rule,  therefore,  which  the  engineer  is  to 
take  as  a  guide,  in  order  to  satisfy  the  condition  of  bringing 
the  exterior  ground  under  an  efficacious  fire  from  the  work,  is 
to  plaa  the  principal  lines  of  his  work  on  tfu  most  command- 
ing point*  of  th<  site,  ami  in  such  directions  as  to  brirftj  the 
anterior  ground  to  b<  swept  in  a  position  sloping  toward  these 
limes;  and  this  will  generally  be  best  effected  by  placing  the 
salient  points  of  the  work  on  the  most  commanding  and  salient 
points  of  the  site  ;  as,  in  this  position  of  the  salients,  the  fa 
which  are  usually  the  principal  lines  bearing  on  the  exterior 
ground,  will  occupy  the  salient  and  commanding  portions  of 
the  site,  whilst  the  re-entering,  being  thrown  on  the  re-enter- 
ing and  lower  portions  of  the  lite,  Will  be  in  the  best  position 
for  sweeping  the  ground  immediately  in  advance  of  the  fa 
and,  at  the  same  time,  they  will  he  masked  by  the  faces  from 
the  enemy's  view,  and  thus  preserved  from  serious  injury  up 
to  the  moment  when  their  action  may  he  rendered  most  effec- 
tive; that  i>  when  the  enemy,  despite  the  fire  from  the  faces, 
has  bucci  eded  in  plauting  himself  upon  points  on  which  this 
lire  cannot  longei  he  brought  to  hear. 

•  ;:» }...•_'<!.    The  condition  of  leaving  no  point  of  the  defences 
unguarded  by  the  fire,  will  depend,  in  a  great  degree,  for  it* 
fulfillment   on  the  same  rule  as  the  preceding.      But    wl 
both  conditions  cannot  bi  1,  the  distant  defence  should 

be  sacrificed  to  the  near,  as  upon  the  latter  the  more  or  ]. 
obstinacy  of  resistance  depends,  since  the  lire  of  the  work  i 
the  action  of  tin   .  are  the  more  effective  as  the  point 

guarded  i*  the  nearer  to  the  .. 

d.     The  condition  that  the  troops  and  '  within 

the  d  shall  he  sheltered  from  the  enemy's  fire,  from  all 

manding  points  without,  will  depend    uj 
tions  of  the  principal  lin<  s  and  the  <  omraand 

point.-;  and  as  far,  '  i  i  he  done,   without  sacri- 

ficing either  of  tl  mportant   conditi 

30 


234  .  INFLUENCE    OF    IKKl  '.11   VRITIKS    OF    Mil:. 

the  plan  of  tin-  work  should  be  bo  arranged  that  the  principal 
linos  shall  present  themselves  in  the  most  favorable  direction 
to  tlir  exterior  ground  to  avoid  plnnging,  enfilading  or  reverse 
views  npon  their  terrepteina  from  any  point  of  it. 

o':W>...To  effect  these  objects,  when  the  work  is  in  the  vicinity 
of  commanding  heights  within  cannon  range,  and  the  crests ol 
these  heights,  as  seen  from  the  work,  present  a  nearly  horizon- 
tal outline,  the  principal  lines  of  the  work,  fronting  the  heights; 
should  receive  a  direction  as  nearly  parallel  as  practicable  to 
that  of  the  commanding  crests;  when  the  outline  of  the  crests 
presents  a  nearly  continuous  line,  but  one  which  declines  or 
slopes  toward  the  site  of  the  work,  the  principal  lines  toward 
the  height  should  receive  a  direction  converging  toward  the 
point  where  the  line  of  the  crests,  as  seen,  if  prolonged  would 
join  the  site. 

The  reasons  for  the  positions  assigned  to  the  principal  lines, 
in  these  cases  respectively,  may  not,  at  a  first  glance,  he  ob* 
vious;  hut,  by  examining  the  relative  positions  of  the  crests 
of  the  heights  and  of  the  principal  lines,  as  here  laid  down,  it 
will,  without  difficulty,  he  seen  that  they  can  be  brought  in 
the  same  plane,  and  the  latter  he  so  placed  as  to  give  a  nearly 
uniform  command  to  the  parapets  of  the  principal  lines  over 
the  site  ;  and  that  by  keeping  the  tenvplcins  of  these  lines  in 
planes  parallel  to  the  one  in  which  the  crests  of  the  heights 
and  those  of  the  parapets  are  held,  and  at  suitable  levels  below 
it,  the  parapets  will  he  made  to  cover  the  tenvplcins  from  the 
fire  of  the  heights  in  the  simplest  manlier. 

G97...T11C  foregoing  general  methods,  for  determining  the 
direction  of  the  principal  lines  fronting  commanding  heights, 
so  as  to  cover  from  direct  fire,  in  the  easiest  manner,  by  their 
parapets,  the  space  to  the  rear  occupied  by  the  troops  and 
materiel,  present,  at  the  same  time,  the  simplest,  cases  of  the 
adaptation  of  the  plan  of  a  work  to  the  features  of  the  locality, 
to  subserve  the  object  in  view.  In  most  cases,  all  that  can  he 
done  is  to  avoid  giving  such  directions  to  any  of  the  principal 
lines  as  shall  he  favorable  to  enfilading  or  reverse  views  of  the 


'    .  INFLUENCE   OF   IRREGULARITIES    OF   SITE.  235 

enemy  ;  which  may  be  effected  by  so  placing  them  that  their 
prolongations  shall  fall  on  points  where  the  enemy  pannol 
till >1  ish  his  works;  or,  on  those  which,  If  occupied  by  him,  will 
afford  disadvantageous  positions  for  bis  batteries,  cither  for 
enfilading  or  reverse  fires. 

G9S...I)uiu  mi  vi  of  I'kkmankm  Works.  The  greater  im- 
portance of  so  adapting  the  plan  and  command  of  permanent 
works  to  the  features  of  irregular  sites  as  to  satisfy  the  condi- 
tions of  sweeping,  thoroughly,  by  their  fire  all  approaches  ex- 
terior to  the  defences,  and  completely  flanking  the  latter,  sel- 
dom places  it  in  the  power  of  the  Engineer  to  fulfil  the  condi- 
tion of  withdrawing  the  interior  of  the  defences  from  either 
enfilading  or  reverse  views  by  a  modification  of  either  the 
plan  or  the  command.  To  shelter  the  terrepleins  which  would 
be  exposed  to  these  tire.-,  as  well  a>  such  as  would  be  attained 
by  a  plunging  lire  in  front.  resoW  must  be  had  to  the  usual 
expedients  of  defilement  ;  that  is,  giving  to  the  terrepleins 
such  positions  with  respect  to  their  parapets  that,  the  troops 
and  materiel  upon  them  will  be  screened  from  a  plunging  fire 
in  front,  by  the  parapets;  and,  when  the  terrepleins  are 

1  to  either  enfilading  or  reverse  view.-,  so  placing  earthen 
traverses  or  other  masks,  as  to  intercept  these  views,  and  cover 
the  troops,  etc.,  from  the  enemy*.-  projectiles. 

699.. .The  defilement  of  permanent  works,  like  that  of  field- 
works,  proposes  the  same  end,  and  employs  nearly  the  same 
means.  They  differ  mainly  in  their  practical  details;  the  lat- 
ter being  reduced  to  a  simple  practical  operation  on  the  held, 
whilst  the  former,  from  the  usually  greater  complexity  of  the 
arrangements  of  permanent  defences,  requires  the  aid  of  tnath- 
itical  science,  and  demands  results  of  i  xtrem< 

"T00...For  the  solution  of  all  probl  the  defileini 

nanent  works,  th<  nires:    1st.  The  limit 

ire  may 
-  -  uncertain  as  to  I.     2d.  The  pre- 

sume within  this  limit  that  the  enemy  up 

to  bring  npon  the  w 


236  iMi.riM  i:  OF   ikin.cri.AKiiii CS   OF  SITE. 

rate  topographical  map  di  all  the  ground  within  the  above 
limil  76D  by  its  horizontal  curves  referred  to  a  plane  of 

comparison.  4th.  The  magiBtrale  and  interior  crests  of  the 
works,  as  either  definitively  or  approximately  arranged,  re* 
ferred  to  the  same  plane. 

701. ..The  limits  beyond  which  the  enemy's  tire,  from  the 
usual  siege  guns,  may  be  disregarded,  owing  to  tin-  uncertainty 
of  long  ranges,  are  L,500  yards,  where  the  work  is  exposed 
only  to  a  direct,  or  front  fire  ;  and  2,000  yards,  when  open  to 
a  reverse  fire.  When  the  terrepleins,  therefore,  are  covered, 
either  by  their  parapets  or  other  means,  from  batteries  at  the>e 
distances,  they  may  be  considered  as  offering  shelters  suffi- 
ciently secure  for  the  troops,  etc.,  upon  them. 

702...H  may  happen  that  there  are  points  beyond  these  limits, 
but  within  the  extreme  rringe  of  siege  gun.'-,  which,  from  their 
positions,  it  would  not  he  safe  to  disregard;  hut  these  will  form 
exceptional  cases,  and,  when  they  occur,  will  be  treated  in  the 
same  manner  as  those  within  the  limits. 

703.. .The  surface  embraced  within  the  limits  and  the  line  of 
defences,  may  be  divided  into  three  zones:  one  lying  between 
the  limits  and  the  position  of  the  first  parallel  of  the  attack, 
which  is  usually  600  yards  from  the  salients  of  the  line  of  de- 
fences; the  second  between  the  positions  of  the  first  and  second 
parallels,  or  to  a  line  within  about  300  yards  of  the  salients 
just  mentioned  ;  the  third  between  the  positions  of  the  Becond 
and  third  parallels,  or  up  to  within  60  yards  of  the  salients. 
In  any  position  that  the  enemy  can  take  up  tor  his  batteries, 
Within  the  first  zone,  it  is  usually  estimated  that  he  will  not 
throw  up  any  parapet  with  a  greater  command  than  10  feet 
over  the  ground  on  which  it  is  placed.  Granting  this,  the 
muzzles  of  his  guns,  behind  the  parapets,  will  not  be  raised 
higher  than  6  feet  above-  the  natural  surface  ;  so  that,  assum- 
ing the  surface  of  this  first  zone  to  be  raised  (!  feet  above  its 
true  position,  this  may  be  regarded  as  the  limit,  vertically, 
within  which  the  enemy's  lines  of  fire  will  be  restricted  ;  and, 
therefore,  if  the  interior  of  the  defences  is  covered  from  the 


TXFiJiM  i:  OF  iKKE<;ri..\i;rrn:s  of  site.  237 

fire  -within  this  limit,  the  troops,  etc.,  will  be  secure.  Tliat  the 
enemy  will  not,  in  all  likelihood,  elevate  his  guns  above  thii 
limit  will  seem  probable,  when  it  is  taken  into  consideration 
that  any  advantage  lie  might  derive  from  doing  so  would  not 
be  commensurate  to  the  labor  it  would  cost  him.  For,  sup- 
pose the  enemy  to  have  taken  op  a  position  for  an  enfilading 
battery  at  1,000  yards  from  any  salient,  to  enfilade  one  of  its 
t'aees  of  the  length  of  100  yards;  and  that  lie  should  decide 
upon  raising  his  gnns  «3  feet,  or  one  yard  above  the  limit  just 
laid  down;  a  simple  proportion  will  show  that,  hy  this  increase 
in  the  height  of  his  battery,  he  will  he  ahle  to  attain  a  point 
at  the  farther  end  of  tlie  face  only  3.<>  inches  lower  than  he 
would  have  done  in  the  position  of  the  assigned  limit;  an  ad- 
vantage which,  considering  the  uncertainty  of  the  fire  at  the 
imed  ranges,  would  hardly  compensate  the  additional  labor 

of  giving  to  his  works  the  additional  command. 

704... In  the  zone  between  the  first  and  second  parallels,  the 
limit  may  ho  reduced  to  4m  feet,  tor  at  this  distance  from  the 
defences  their  fire  is  s<>  destructive  and  certain  that  the  enemy 
cannot,  without  great  loss  of  life  and  time,  raise  the  parapet 
of  his  batteries  higher  than  8  feet  above  the  natural  surface. 

705... From  the  third  lone,  the  musketry  of  the  enemy  may 
he  brought  t<>  hear  upon  the  defence- ;  and.  from  this  position, 
during  sortie-  from  the  defence-,  or  at  any  other  opportune 
moment  when  their  tire  is  not  active,  the  enemy  might  mount 
on  the  parapet  of  his  trenches,  ami  from  there  deliver  his  tire. 
This  would  bring  his  line  of  fire  about  1"  feet  above  the  na- 
tural surface.  The  limit,  vertically,  of  tl,  may,  th< 
fore,  he  assumed  at  10  feel  above  the  natural  surfs 

706.. .The  limits  of  the  dangerous  ground  exterior  to  the  line 
of  d(  may  he  marked  off  on  the  topographical  map  of 

the  site,  PI.  7.  Km.  1.  by  drawing  lines  concentric  with  the 
line  ting   the   most   advanced 

and  at  tl  m  it  of  1,500  OF 

iic  tire  may  lie  brought  to  hear  on  the  front   oi 
yards:  300  \  .ml- :  ami  6< '  J  ards;  and  tl 


238  l.M'i.ri:N<  i;   OF   EBBSGULABITIES   OF   BITE. 

once?  of  the  horizontal  curves  of  the  ground,  within  the  zones 
thus  marked  off,  to  be  increased  <>  feel  in  the  lirst;  4.5  feet  in 
the  second;  and  LO  feet  in  the  third. 

707...In  the  defilement  of  each  part,  separately,  of  the  line 
of  defences,  those  portions  alone  of  these  zones  should  be  re- 
garded as  dangerous  which  are  embraced  within  arc.-,  or  other 
lines  drawn  at  the  foregoing  distances  from  the  salients,  or  the 
laces  of  the  ]>art  to  be  defiled.  It  may  also  happen  that,  within 
the  limits  of  dangerous  ground  for  one  portion  of  the  line  of 
defences,  there  may  be  other  portions  which,  from  their  posi- 
tion, may  mask  the  portion  to  he  defiled  from  all  the  danger- 
ous points  beyond  them  ;  in  which  case  the  points  thus  shut 
off  need  not  be  regarded,  in  effecting  the  operations  of  de- 
filement. If,  for  example,  PI.  7,  Fig.  1,  the  limits  of  danger- 
ous ground  for  the  demilune  A  being  marked  oh",  it  is  found 
that  the  demilune  B  masks  the  demilune  A  from  all  fire  that 
might  come  from  the  ground  beyond  B  ;  then  this  portion  of 
the  zones  of  danger  need  not  be  regarded  in  defiling  A.  To 
ascertain  this  point,  it  will  be  only  necessary  to  conceive  a 
right  line  to  be  so  moved  as  to  rest  in  each  of  its  positions 
upon  a  point  of  the  interior  crest  of  .1  and  on  one  of  B  j  and 
if  this  line,  in  all  its  positions,  passes  above  the  surface  of  the 
dangerous  zones  beyond  B,  then  will  B  serve  as  a  mask  for  .1. 

708. ..In  covering  masonry  from  the  enemy's  artillery,  800 
yards  is  usually  regarded  as  the  longest  range  at  which  de- 
structive effects  can  be  produced ;  and,  also,  that  within  this 
distance  the  angle  of  incidence  of  the  ball  on  the  surface  must 
be  greater  than  45°,  to  do  serious  injury  to  it. 

709.. 4*i  the  defilement  of  works  of  limited  interior  capacity, 
as,  for  example,  the  redoubt  of  the  reentering  place  of  arms, 
the  double  caponniere,  and  the  like,  which  are,  moreover,  not 
habitually  occupied  by  troops,  the  extreme  limits  may  be  re- 
duced to  l,iMiil  ,,r  l.-jmi  yards. 

710...  Within  the  limits  of  the  zones  of  danger,  positions  may 
be  found  for  direct  or  front,  for  reverse,  and  for  enfilading  tire. 
If  the  twro  faces,  for  example,  of  a  work  be  prolonged  to  in- 


iNFi.rr.Ni'i:  OF  11:1:1  OUL  \i:n n  a  Of  sin:.  239 

tersect  the  extreme  limit  ofdangerous  ground,  the  Bector  which 
they  embrace  may  be  termed  the  limits  of  direct  or  front  fire f 
since,  from  every  position  that  can  be  taken  up  within  this 
sector,  a  direct  fire  alone  can  be  brought  to  bear  upon  the  two 
faces.  The  two  sectors  which  lie  adjacent  to  this  may  be 
termed  the  limits  of  lateral  or  reverse  fire,  since  they  afford 
positions  from  which  a  reverse  fire  can  be  obtained  againsl 
one  of  the  faces,  and  a  front  fire  upon  the  other.  It  is  also 
only  -within  these  last  limits  thai  positions  for  enfilading  the 
terrepleins  of  the  faces  can  he  obtained. 

711. ..The  problems  of  defilement  which  present  themselves 
for  solution  may  embrace  one  or  more  of  th-  -  in  any 

example;  depending  upon  the  relative  positions  of  the  interior 
crest  of  the  work  to  he  defiled,  and  of  the  dangerous  ground 
embraced  within  the  foregoihg  limits.  In  the  case  of  only  di- 
rect fire,  the  terrepleins  can  he  screened  by  their  parapets 
alone;  in  that  of  a  reverse  tire  on  one  face  alone,  its  terre- 
plein,  in  some  cases,  may  be  screened  by  a  suitable"  position 
given  to  the  parapet  of  the  other;  where  both  are  exposed  to 
this  fire,  one  or  more  traverses  must  be  resorted  to  as  a  screen; 
against  an  enfilading  fire  on  one  face  alone,  a  portion  of  the 
parapet  of  the  ether,  near  the  salient,  may  he  a  sufficient  pro- 
tection  in  Borne  cases  :  but,  for  the  most  part,  traverses,  placed 
across  the  terreplein,  will  he  the  only  remedy. 

712...  It  does  not  cotne  within  the  ^mjir  of  thi-  summary  t<> 
examine  the  many  cases  of  defilement  which  may  arise  from 
irregularities  in  the  site ;  those  alone  will  he  discussed  which 
are  of  most  ordinary  occurrence,  and  which  require  for  their 
solution  the  usual  geometrical  constructions  involved  in  tan- 
gent and  .-cant  planes  and  other  surfaces,  to  a  surface  defined 

by  the  projection  of  its    horizontal    curve.-.      The    i  hich 

will  here  find  their  application  may  he  arranged  under  two 
head-:  1st,  the  plan  and  command  of  a  work  being  definitely 
decided  upon,  to  ascertain  t1  portions  of  'he  z. >n. 

danger  from  which  any  description  of  tire  can  he  brought  to 
hear  upon  it.-  terrepl  ins,  and  to  defile  them  from  it ;  i'd,  the 


240  INFLUENCE   OF   IRREGULARITIES    OF    SITE. 

plan  of  a  work  being  definitely  fixed,  but   its  command  only 
approximately  within  certain  limits,  to  ascertain  the  eaei 
method  of  defiling  the  terrepleins  of  the  work  by  varying  the 
command,  or  position  of  the  interior  crest,  within  the  assigned 

limits. 

!T13...Pbob.  1,  Pl.  7,  Fio.  2.     The  command  or  position  of 

ih'    int<  rior  <■/■<  *Ay  of  the  facts  of  a  work  b<  ing  v'-v<  <L  to  aso  r- 
tain  tin  dangerous  points  on  th<  exterior,  and  to  defiU  its  t>  r- 
r&plein  from  t/ccse  points. 
Let  a b,  a c,  be  the  projections  of  the  given  crest;  and  the 

curves  (28. 0),  (29.0),  etc.,  those  of  the  natural  surface. 

Prolong  outward  to  c  and  d,  the  faces  ;  construct  the  scales 
of  declivity  of  the  two  lines  ae,  ad;  and,  from  them,  the 
scale  of  declivity,  ef,  of  their  plane.  From  the  salients,  sup- 
posing an  arc  to  be  described  with  a  radius  of  1,500  yards,  the 
dangerous  ground  will  be  included  between  it  and  the  two 
faces  of  the  work.  Now,  if  the  plane  of  the  interior  crests,  of 
which  ef  is  the  scale  of  declivity,  be  indefinitely  extended; 
and  its  intersection  with  the  surface  parallel  to  the  natural 
surface  and  0"  feet  above  it  be  found,  it  is  evident  that  the  por- 
tion of  this  raised  surface  which  lies  below  the  plane  may  bg 
disregarded,  as  no  fire  from  it  can  have  a  plunge  upon  the  in- 
terior of  the  work.  But,  from  every  point  of  the  surface 
above  the  plane,  a  plunging  fire  can  be  brought  to  bear  on  the 
terreplein.  Having  drawn  the  horizontals  of  the  plane  ef, 
and  found  their  intersections  with  the  corresponding  horizon- 
tals of  the  raised  surface  (which  last  will  be  given  by  adding 
0  feet,  or  2  yards,  to  the  references  of  the  curves  of  the  ground), 
of  which  xy  z  is  the  projection.  That  portion  of  the  surface. 
which  lies  above  this  curve  will  alone  have  a  plunging  tire 
upon  the  work,  and  will  be  the  only  portion  for  which  defile- 
ment will  be  necessary. 

Now,  as  this  intersection  falls  entirely  within  the  angle  d  a 
e  of  the  faces  prolonged,  or  within  the  limits  of  front  fire,  it  is 
evident  that  the  terrepleins  will  require  to  be  defiled  only 
from  direct  fire. 


INFLUENCE   OF    IRREGULARITIES    01    SHE.  241 

To  effect  this,  let  a  plane  be*  passed  through  the  face,  J,  a  d, 
of  the  work,  and  tangent  to  the  raised  surface  above  x  yz. 
Tin's  plane  will  pass  above  all  the  dangerous  ground,  excepl  at 
its  poinjfc  of  contact  with  it;  and,  being  extended  -back  from 
the  face  within  the  work,  it  is  clear,  if  the  terreplein  of  this 
face  be  so  taken  with  respect  to  this  plane  that  no  point  of  it 
shall  he  less  than  8  feel  below  the  plane,  that  then  every  point 
of  the  terreplein  will  be  screened  tVom  a  plunging  fire  by  the 
■parapet  of  the  lace  a  h.  Now,  if  the  same  series  of  operations 
be  gone  through  with  for  the  face  c  a  e,  then  will  its  terreplein 
be  defiled  in  Like  manner;  and  thus  the  defilement  of  the 
whole  work  be  completed  for  this  ease. 

The  tangent  planes  which  satisfy  the  above  condition  are 
termed  Planet  of  Direct  Defilement,  and  they  may  be  defined 
as  planes  which,  passed  through  tin  interior  crest  of  apwrape% 
learn  at  least  6  feet  below  them  ail  the  dangerous  ground  <>f 
front  Jire,  and  pass  at  lea/si  8  feet  above  every  point  of  ilu  t<  r- 
replein  behind  tht  parapet. 

The  terrepleins are  usually  parallel  to  their  respective  plai 
of  direct  defilement,  and  8  feet  below  them.     13ut  when  the 
declivity  of  the  plane  of  defilement  exceeds  1-25,  then  the  teiv 
replein,  if  it  is  to  receive  cannon,  must   be  kept  within    this 
limit. 

In  the  Fig.  •_',  the  references  are  put  down  in  yards.  The 
tangent  plane  through  b  a  d  is  determined  in  the  usual  man- 
ner, by  finding  the  horizontal  (in  th  30.0),  among  all 
those  drawn  to  the  curve-  of  the  raised  surface)  which  ma 
the  mimimum  angle  with  b  <L  The  line  /<  /,  perpendicular  to 
this  horizontal,  is  the  Bcale  of  declivity  of  this  plane;  and  the 
point  J?,  that  of  contact.  The  Line  k  I  is,  in  like  manner,  the 
of  declivity  of  the  other  plane,  and  <>  its  point  of  conj 

71 4  —  It  might  happen,  from  the  steepness  of  the  terrepleins, 
that  the  reentering,  or  gutter,  formed  at  their  intersection, 
would  be  inconvenient,  and  it  would,  thi  ••  desirable 

to  have  this  portion  raised,  when  it  can  be  done  without 
posure  to  a  plunging  lire.     This,  in  m< 


242  l.MIM.N.i     01    LRBBGULABrnSS    >.|     SITE. 

iii  this  way.  It  will  be  seen,  from  Bn  inspection  of  the  V 
that  the  points  o  and  p  are  the  only  ones  from  which  the 
enemy's  fire  pass*  -  i  jcactly  al  8  feet  above  all  the  points  of  the 
respective^ terrepleins  determined  by  the  tangent  planes;  and 
that  if,  from  these  points,  lines  of  fire,  o  a  r  and  p  a  «,  be 
drawn,  every  other  line  of  fire  through  </,  from  the  ground  in 
the  angle p  a  o,  will  pass  more  than  8  feet  abov^e  the  portion 
of  the  terrepleins  embraced  in  the  angle  s  a  r,  since  the 
ground  within  the  exterior  angle  lies  below  the  tangent  planes. 
If,  then,  a  be  taken  as  the  verliex  of  a  cone,  tin*  elements  of 
which  arc  tangent  to  the  raised  surface  within  the  angle p  a  <>, 
and  if  these  elements  be  prolonged  within  the  work,  their  pro- 
longation will  form  a  cone  of  lines  of  fire,  which  will  pass 
more  than  8  feet  above  the  terrepleins.  If  these  last,  there* 
fore,  be  connected  by  a  surface  parallel  to  this  cone,  and  8 
feet  below  it,  this  surface  may  be  taken  as  the  portion  of  the 
tefreplein  which,  connecting  the  two  plane  portions,  will 
remedy  the  inconvenience  pointed  out. 

715...P&OB.  2,  Fig.  8.  The  data  being  the  sanu  as  i»  the 
preceding  oase,  and  thewoflc  being  exposed  to  both  direct  and 
reverse  vu  mw,  to  oov'er  its  interior  from  thest  vi*  ws. 

Suppose  the  plane  of  the  interior  crest  of  the  faces  extended 
within  the  limits,  and  its  intersection  with  the  dangerous 
grbund  determined,  as  in  the  preceding  case;  and  let  x  y  0,  vi 
n  0  and  J?  q  r  be  the  curves  of  this  intersection. 

The  face  a  b  will  be  exposed  to  direct  fire  alone  from  the 
ground  above  the  two  curves,  x  y  z  and  m  n  0,  and  to  reverse 
fire  from  that  above  the  curvey  q  r.  In  like  manner,  the 
face  a  c  will  he  exposed  to  direct  fire  from  X  ;/  3  and  p  q  r, 
and  to  re\  erse  fire  from  m  »  o. 

The  defilement  of  each  face,  from  the  direct  fire,  will  be 
effected  jprecrsely  in  the  same  way  as  in  the  preceding  problem, 
The  lines  //  i  and  k  I  are  the  scales  of  declivity  of  the  planes 
of  direct  defilement  of  the  faces  respectively1. 

For  the  reverse  defilement,  a  plane  is  passed  through  a  b, 
tangent  to  the  surface  above p  q  >• ;  and  one  through  a  <\  tan- 


INFLUENCE    OF    IKIM.i ;!  I.AKI'l  IKS    OF    SITE.  243 

gent  to  the  surface  above  //,  ?i  0,  and  their  line  of  intersection 
a  a'  found.  The  line  u  v  is  the  scale  of  declivity  of  one  of 
these  planes,  termed  a  Plane  of  Revem  Defilement^  and  s  t 
that  of  the  other. 

Now,  if  a  traverse  is  so  placed  that  its  crest  shall  occupy 
the  position  of  the  line  a  a',  it  will  coverall  between  it  and 
the  two  faces,  as  high  as  the  interior  crests,  from  the  reverse 
fire  on  each  side.  But  as  it  is  desirable  to  have  the  troops, 
when  «m  the  banquettes,  screened  from  this  fire,  the  crest  of 
the  traverse  should  he  raised  from  18  inches  to  2  leet  ah 
the  line  Q  <t\  to  effect  this. 

The  traverse  should  extend  so  far  toward  the  gorge  of  the 
work  that  the  entire  line  of  each  face  shall  be  covered  by  it. 
To  determine  its  length  with  this  condition,  lines  are  drawn 
from  the  extreme  point,  b  and  c,  of  the  faces,  tangent  to  the 
curves  m  n  <>  ami  p  <j  /•,  and  their  points  of  intersection  with 
narked;  the  one  that  falls  farthest  from  the  salient,  will 
evidently  give  the  required  length. 

If  the  line  a  a',  should  fall  so  near  either  of  the  faces  that 
.  if  placed  along  it,  would  incommode  the  service 
of  that  part  of  work,  it  will  be  best  to  place  it.-  eiv.-t  in  the 
■vertical  plane  a  a"  of  the  capital  of  the  work.  When  M 
placed,  the  intersection  of  tin.-  vertical  plane  with  each  of  the 
planes  of  reverse  defilement  must  he  found,  and  the  crest  of 
the  traverse  he  taken  i  8  inches  above  the  one  that  lies  highest. 

716.. .The  position  of  th<  ifthetra  rmined 

by  either  of  the  preceding  methods,  will  he  in  a  vertical  plane 
passing  through  the  salient  </  of  the  work.     Prom  the  thici 
and   slopes  which  travetWi  usually  receive,  they  would  ordi- 
narily, if  placed  in  this  position,  take  up  ail    the  inter' 
within  the  salient,  and   have   no  room   there   for  disposit 
either  for  artillery  or  musketry.     To  .prevent  thi  ik  is 

made  in  the  direction  of  the  ie  point  on  | 

plane  through  the  salient,  from  which   it   \>  «. 

.:•  tron i    | 

cient  room  will  b  In  th 


2-14  ini  ill  N<  i:    OF    IKEEOTJl  \i:mi:s   OF   BITE. 

which  illustrates  this  arrangement,  tlie  traverse  is  withdrawn 
far  enough  from  the  salient  to  leave  room  for  a  barbette  bat- 
tery for  several  gun:-. 

The  laee  upon  which  the  traverse  is  directed,  will  be  deter- 
mined by  the  condition  of  covering  both  faces  in  the  most 
effective  manner,  by  the  position  taken  for  the  traverse. 

717. ..The  cross  section  of  traverses  for  permanent  works  is 
similar  to  those  used  in  field-works.  The  top  of  the  traverse1 
receives  a  slight  slope  each  way  from  the  crest  to  the  sides. 
The  thickness  at  top  is  from  12  to  20  feet,  to  render  it  shot- 
proof.  The  sides  take  the  natural  slope  from  the  top,  either  to 
their  intersections  with  the  planes  of  direct  defilement  or  to 
the  terreplein.  If.  to  gain  interior  space,  these  slopes  are  ter- 
minated at  the  planes  of  direct  defilement,  then  the  portions 
of  the  traverse  below  these  planes  are  made  more  steep,  and 
the  earth  supported  by  retaining  walls.  The  top  of  the  trav- 
erse, where  it  joins  the  parapet,  being  higher  than  the  superior 
slope,  is  run  out  above  this  slope,  upon  which  the  side  slopes 
tall ;  its  extremity  terminates  in  the  plane  of  the  exterior  slope, 
extended  above  the  exterior  crest. 

718. ..Traverses  may  be  arranged  for  bomb-proof  shelters 
and  musketry  defence,  by  throwing  a  bomb-] .roof  arch  be- 
tween the  side  retaining  walls,  and  piercing  the  wall  hearing 
on  the  portion  of  the  terreplein  which  will  first  fall  into  the 
enemy's  power  with  loop-holes. 

7l:i...\\'hen  from  any  circumstance,  a  single  traverse  cannot 

be  used,  for  reverse  defilement,  resort  must  he  had  to  several, 
which  should  he  so  combined  that  no  line  of  lire  can  pene- 
trate between  their  extremities  to  attain  any  point  which  they 
should  cover.  The  examples  of  like  combinations  given  in 
the  Front,  will  readily  suggest  the  manner  of  making  others^ 
of  which  farther  illustrations  will  be  found  in  the  following 
ease. 

720. ..Where  a  demilune  is  arranged  with  a  redoubt,  a  tra- 
verse placed  in  its  salient  cannot  be  extended  farther  hack 
than  the   counterscarp  of  the  redoubt,   and  an -open    space, 


INFLUENCE  OF   IRREGULARITIES    0¥   BITE.  245 

therefore,  will  lie  left  at  the  ditch,  through  which  a  reverse 
fire  would  attain  that  portion  of  either  face  which  is  not  cov 
ered  either  by  the  traverse  in  the  salient  or  by  the  parapet  of 
the  redoubt  To  cover  the  part  thus  exposed,  it  will  he  n< 
sarv  to  place  one  or  more  traverses  which,  in  combination  with 
the  one  in  the  salient  and  the  parapet  of  the  redoubt,  shall 
subserve  this  end. 

To  simplify  the  case,  let  the  face  a  <?,  PI.  7.  Fig.  5,  he  the 
one  exposed,  and  let  the  point  x  be  one  the  fire  of  which  is 
most  dangerous.  Having,  in  the  first  place,  arranged  the  tra- 
verse t.  as  in  the  last  example,  and  drawn  the  two  lines  of  fire, 
0 b  and  x  d,  from  the  point  ./%  through  the  extremity  of  the 
traverse  and  the  top  of  the  parapet  of  the  redoubt  at  the 

salient,  the  length,  h  <L  of  the  face  intercepted  between  these 
lines  will  he  the  part  to  he  covered.  It'  a  second  traverse,  1\ 
he  placed  across  the  terreplein  of  the  other  face  of  the  demi- 
lune, and  in  a  position  such  that  one  of  its  ends  shall  real  on 
,/•  />.  and  the  other  on  x  </.  it  will    evidently    cover   the   portion 

bd. 

721. ..In  selecting  the  positions  of  several  Combined  trave: 
attention  muBt  be  given  to  avoid  those  where,  if  one  be  placed) 
the  enemy  would  lind  shelter  behind  it  from  the  fire  in  the 
rear.    Tn  the  example  just  taken,  the  slope  of  f.  toward  the 

salient,  should  be  swept  by  the  fire  from  the  rear,  through  the 

redoubt  ditch  ;  the  Hke  slope  of  t  should  he  swept  by  a  por- 
tion of  the  redoubt  face  mar  it-  salient  :  and  neither  &0  Pail  as 
to  have  tin    sp ace  behind  it  masked   from  tire  by  the  one  t 
rear. 

722...Trav<  rs<  -  usually  pn  Bent  not  only  the  :,,n 

of  all  problen  i  rse  and  enfilading  defilement,  hut.  afford- 

ing the  means  of  rendering  the  command  independent  of 
tire  from  without,  they  enable  the  engineer  t..  regulate  this 

ly  with  a   view  t..  the  effect  which  lie  d( 
attain   by   his   own   fire.      From   the   -  ■  ,r   the  ,r 

"ion.   tra  ,iy.  a-  in  tic  f  narrow  ten 

like  those  of  the  Inne   with   a 


246  infi  i  !  n<  1:   OF   rRREGULAMTTRS  OF   BIT*. 

redoubt,  be  inconvenient,  1  >< >tli  from  embarrassing  the  commu- 
nications ami  from  taking  up  ground  that  may  be  wanted  for 
batteries. 

r23...Pa08.  ■'*.  Tht  plan  of  a  bastion  being  definitively  fioaed\ 
and  cm  point  of  it*  comma ml  approximately,  A<  <hjil<  fh< 
workinthi  most  advantageous  manner,  by  nJii/t'nty  tlie  post* 
fion  <>/  Us  interior  crest  within  certain  Hunt*. 

Let  Fig.  6  be  tke  plan  of  the  work,  and  a  the  salient,  tin* 
command  of  which  can  be  varied  within  certain  limits,  with- 
out impairing  any  of  the  other  conditions;  arid  let  the  danger* 
ous  ground  be  embraced  within  the  arc m  »,  at  1,500  yards 
from  a,  and  the  lines  a  il  and  a  o  supposed  drawn  from  a, 
through  covering  masses  on  the  right  and  left  of  the  work. 

The  front  limits  of  defilement  in  this  case  are  embraced 
within  the  sector  m  a&i  /  and  the  lateral  limits  within  the 
other  two,  m  a  u  and  n  a  v.  Now,  the  most  favorable  ease  of 
defilement  here  will  be  that,  where  a  plane,  containing  a  taken 
within  its  extreme  positions,  shall  pass  above  all  the  exterior 
ground,  and  give  such  a  command  to  the  interior  crest  through- 
out, when  held  in  it,  as  shall  satisfy  the  other  conditions  of  de- 
fence. To  ascertain  the  existence  of  such  a  plane,  let  a  be 
taken  as  the  vertex  of  a  cone  which  envelops  all  the  danger- 
ous ground,  any  plane  tangent  to  this  cone  will  satisfy  the 
condition  of  defilement,  ami  it  will,  therefore,  only  be  necessary 
to  find  whether  any  one  of  these  planes  of  defilement  will  satisfy 
the  other,  of  giving  the  points  />,  *'.  d  and  <■  a  suitable  command. 
If  no  such  plane  can  be  obtained,  the  next  most  favorable  case 
will  be  to  find  one  that  shall  satisfy  all  the  requisite  conditions 
of  command,  and  intersect  the  ground  only  within  the  front 
limits.  In  this  case  it  is  clear,  from  tin-  position  of  this  plane, 
if  the  interior  crests  are  held  in  it,  that  the  interior  of  the 
work  will  be  exposed  only  to  the  direct  fire  from  that  portion 
of  the  ground  which  lies  above  the  plane. 

Let  xy  z  be  the  curve  of  intersection  of  the  plane  with  the 
ground,  found  in  the  usual  way.  Through  the  faces  a  b  and  a 
d,  let  planes  of  direct  defilement  be  passed ;  the  terrepleins  of 


IM  i  i  I  n<  r    01     11:1:1  (.!  I.AKITIKS    <>K    81TB.  L'I7 

the  faces  being  held  parallel  to  them  Will  be  covered  by  their 
respective  parapets  from  all  plunging  fire.  But,  in  order  that 
the  planes  of  defilement  of  the  faces  shall  also  defile  the  flanks, 
it  is  necessary  that  each  flank  be  placed  in  the  plane  of  defile- 
ment of  the  adjacenl  face,  and  its  tenreplein  in  that  of  the  tor- 
replein  of.the  face.  Now,  in  giving  the  interior  crests  of  the 
flank-  these  new  positions,  they  will  lie  below  the  plane  that 
contains  the  curve  X y  s,  and  ill'  which  the  mterior  crests  of 
the  faces  lie.  This  being  the  case,  it  may  happen  that  the 
parapet  of  one  of  the  flanks  will  not  cover  the  opposite  face 
from  reverse  fire,  coming  from  the  lateral  limits  opposite  the 
flank.  Tn  this  contingency  it  will  be  necessary,  in  order  to 
cover  the  lace,  to  place  the  flank  in  the  plane  of  the  curve  ,r  y 
.7,  as  this  plane  defiles  from  the  lateral  limits:  but,  in  doing 
this,  the  flank  <1  < .  for  example,  will  be  exposed,  in  its  turn,  to 
the  ground  above  s»ys/  and  to  cover  it,  the  only  remedy  is 
to  erect  a  traverse,  at  some  suitable  point,  which  shall  inter- 
cept all  this  dangerous  fire.  The  least  inconvenient  position 
for  the  traverse  will  usually  be  at  the  shoulder  angle.  From 
this  point,  it  must  extend  so  far  hack  as  to  intercept  all  fire 
from  above  x  y  ~.  botb  on  the  terrepleina  of  the  flank  and  cur- 
tain, where  they  unite, and  be  high  enough  to  screen  the  tro 
on  the  banquette. 

If  the  defilement  cannot  be  effected  by  either  of  these  pro- 
-,  there  remains  no  other  means  than,  having  fiivt  defi- 
nitely fixed  the  command,  to  devide  the  bastion  by  a  trav< 
either  along  its  capital  or  some  other  convenient  direction, 
and.  having  given  it  a  suitable  height,  t<>  covm  each  portion 
from  direct  tire  by  the  usual  method. 

7-1. ..Tin-  foregoing  problemi  embrace  in  their  solution  all 
of  the  more  ordinarv  cases  of  defilement,  and  suLrLrc~t  the  ,. 

to  be  followed    in    treating   Others.      In    all  'de- 

ment of  combined  works,  like  the  enceinte  mid   it-  outwo 
.    it    must   h'-   home    in    mind    that    the   advanced    \\ , 
which,  from    their    |  must   first  'fall    into   the    i 

power,  become  thus  a  portion  of  4he  dangerous  ground  for 


248  IM-I.I   l..\i  I.    o|'    lKKl.ol  I.AKllll.S    OF    Mil:. 

works  more  retired,  and  which  must  also  be  held  after  the  fall 
of  tin-  others.  The  retired  works,  under  such  circumstaa 
must  be  defiled  from  the  advanced;  their  planes  of  defilement 
being  made  to  pass  from  •".  feel  to  l..">  feel  above  tin-  portion  of 
the  advanced  work  on  which  it  is  presumed  the  enemy  may 
make  a  lodgment,  ami  which,  from  its  position,  may  be  re- 
garded as  the  most  dangerous  to  tin-  retired  work,  it  is  ac- 
cording to  this  role  that  the  redoubt  of  the  reentering  place  <>t' 
arms  is  defiled  from  tin-  parapets  of  the  two  adjacent  demi- 
lunes; its  plane  i>t'  defilement  extended  outward,  passing  at  ."> 
feel  above  the  salients  of  these  works.  The  tenaille,  in  like 
manner,  is  defiled  from  the  upper  terreplein  of  the  demilune 
redoubt,  as  the  tenaille  must,  he  held  after  the  enemy  has 
established  himself  on  this  terreplein.  For  like  reasons,  the 
nmre  retired  portions  of  the  covered-ways  are  defiled  from  the 
enemy's  lodgments  on  the  glacis  of  the  demilune  salient  place 
of  arms. 

7i;r>...  Where  a  work  has  considerable  command,  and  is  open 
at  the  gorge,  like  the  cavalier  retrenchments,  for  example,  ami 
the  works  in  its  rear  do  not  mask  its  interior  from  reverse  lire, 
it  may  he  necessary  to  place  the  traverse,  termed  aparadosi 
acrof  replein  at  the  gorge,  giving  it  sufficient   height 

to  subserve  the  end  in  view. 

T26...The  methods  of  defilement  here  laid  down  are  those 
now  followed  by  engineers.  They  unite  mathematical  accu- 
racy in  results,  with  great  simplicity  of  detail;  and  render  the 
defilement  altogether  secondary  to  the  other  conditions  of  de- 
fence, upon  which  the  plan  and  command  are  made  essentially 
to  depend.  Before  they  were  adopted,  the  results  of  the 
method  then  followed  were,  in  most  respects,  like  those  ob- 
tained in  the  practical  operations  for  defiling  lield-works.  A 
line,  the  position  of  which  was  determined  by  a  series  of  trials, 

having  for  their  objeel  to  obtain  the  most  satisfactory  results, 
both  as  to  the  economy  oi  the  requisite  embankments  and  the 
best  disposition  of  command  of  the  various  parts  at  or  in  rear 
Of  the  gorge  of  the  work  to  b%  defiled;  this  position  coinciding 


INFLUENCE   OF  IRKFOn.AKTTTl  s   OF   STTK.  24f) 

with  the  natural  Burface,  or  being  above  or  beneath  it,  as  the 
case  required.  Througli  this  line  a  plane  was  passed  tangent 
to  the  dangerous  ground.  This  plane,  termed,  as  in  field  de- 
filement,  a  Rampant  Plane,  was  taken  as  the  artiiicial  site  of 
the  work,  in  reference  to  which  the  relative  command  of  all 
the  ] >arts  was  arranged  as  upon  a  horizontal  site.  Or,  in  other 
words,  the  result  was  nearly  the  same  as  if  the  works  had  been 
arranged  on  a  horizontal  site,  and  then  the  whole  combination 
turned  aronnd  some  fixed  line  of  this  site,  until  it  was  brought 
into  the  position  of  the  required  rampant  plane.  The  defects 
of  this  method  are  evident  at  a  glance.  It  preserves  the  rela- 
tions of  defence  of  the  various  works  the  same  as  in  a  horizon- 
tal site;  but  it.  to  a  great  extent,  leaves  out  of  consideration 
Ae  bearing  of  the  command  on  the  exterior  ground,  and,  in 
many  cases,  may  lead  to  excessive  excavations  and  embank- 
ments which  the  methods  now  followed  enable  the  engin 
for  the  most  part,  to  avoid. 

7_7...Ki  MAi.-K-.  In  the  preceding  discussions  it  will  be  ob- 
served that  the  limits  of  defilement,  horizontally,  have  been 
based  Upon  the  range  and  presumed  accuracy  of  tire  of  artil- 
lery and  small  arms  before  the  changes  which,  within  a  few 
years  back,  have  taken  place  in  both  these  particulars,  and 
which — from  tin-  zeal  ami  intelligence  with  which  experiments 
are  now  being  carried  on,  in  every  part  of  the  civilized  world. 
on  the  forms  of  cannon  and  projectiles  and  the  quality  of 
powder — will,  in  all  probability,  be  extended  and  lead  to  still 
more  remarkable  results.  These  improvements,  however,  will 
have  no  other  effect  upon  the  rules  and  modes  of  d<  ill'  I 
now  in  use  than  to  change  the  limit-,    hi  rrc- 

spond  with  the  ii  of  projectiles.    80  far  ai 

improvement  in  the  accuracy  of  tire  is  concerned,  it  will  ren- 
der a  strict  defilement  of  all  parts  of  the  interior  of  a  work] 
more  imperative,  and   will  lead  engineers  t..  resort  I 

ins  by  which  the  troo  be  hidden  from 

an  enemy's    \  ;<  W  within  the  extreme  1 
to  t1  //  limits,  th( 

32 


250  MINES. 

for  changing  those  now  established.  "When  it  is,  also,  taken 
into  consideration  that  the  relative  command  and  plunge  of 
heights  decrease  with  their  distance  from  the  work  defiled,  and 
also,  that  the  accuracy  of  aim  is  greatly  affected  by  the  same 
cause,  it  is  questionable  whether  any  considerable  extension 
of  the  limits  hitherto  laid  down  will  be  necessary,  except  in 
marked  cases  of  locality. 


MINES. 


728.. .The  subject  of  mines  admits  of  a  division  into  five  parts : 

1st.  The  nomenclature. 

2d.  The  results  of  experiments,  and  the  theory  founded  on 
them. 

3d.  The  manner  of  using  mines  in  the  attack  and  defence. 

4th.  The  conditions  to  which  mines  should  be  subjected  in 
their  arrangement  and  uses. 

5th.  The  construction  or  details  of  the  practical  operations. 

To  these  may  be  added  a  sixth  part,  comprising  the  uses  of 
mines  in  temporary  works. 

729. ..Nomenclature.  The  term  mine  is  applied  both  to  the 
underground  excavations  charged  with  powder  for  the  purpose 
of  producing  an  external  explosion,  and  to  the  communications 
which  lead  to  these  exra  vat  ions. 

The  excavation  in  which  the  charge  of  powder  is  lodged  is 
termed  the  chamber.  The  pit  formed  by  the  explosion  is 
termed  the  crater. 

The  form  of  the  crater  in  ordinary  soils  has  not  been  exactly 
ascertained.  The  only  use  of  the  exact  determination  of  this 
form  would  be  to  calculate  precisely  the  quantity  of  earth 


v  MrNE8.  251 

thrown  from  the  crater,  and  by  that  moans  to  proportion  the 
charge  to  the  effect  to  be  produced.  Different  figures  have 
been  assigned  by  engineers,  to  this  solid;  some  assuming  it  to 
he  a  cone,  of  which  the  centre  of  the  powder  was  taken  as  tile 
vertex;  others,  a  paraboloid,  of  which  die  centre,  of  the  pow- 
der was  the  focus.  To  afford  a  uniform  and  simple  rule  for 
calculating  the  volume  of  the  crater,  the  solid,  PL  A.  Fig.  3, 
is  assumed  to  be  a  truncated  cone,  the  radius,  0  dy  of  the  lower 
circle  being  one-half  the  radius,/?  5,  of  the  upper  circle.  The 
radius p  b,  of  the  upper  circle  is  termed  the  craU  r  radius.  The 
line,  o  ]>,  drawn  from  the  centre  of  the  powder  perpendicular 
to  the  surface  where  the  explosion  takes  place,  the  line  (f  least 
resistance.  The  line,  q  bt  drawn  from  the  same  centre  to  any 
point  in  the  circumference  of  the  upper  circle,  the  radius  of 
explosion. 

The  term  oommon  /><<>"  is  applied  to  a  crater  when  its  radius 
|iial  to  the  line  of  least  resistance.  When  the  crater  radius 
is  greater  than  the  line  of  least  resistance,  the  terms  ,,,>,,- 
oharged  mine  and  globe  of  compression  are  used.  When  the 
crater  radius  is  less  than  the  line  of  least  resistance,  the  mine 
is  termed  undercharged.  A  small  mine  with  a  line  of  least 
n  distance  not  greater  than  9  leer,  which  is  formed  by  sinking 
a  shaft  from  the  surface  of  the  ground,  is  termed  a /">"/• 
The  term  camoufiel  is  applied  to  small  mines  used  to  suffocate 
the  enemy's  miner  without  producing  an  external  explosion. 

The  underground  communications  required  for  the  service 
of  mines  are  termed  galleries.  The  galleries  are  either  arched 
communications  of  masonry,  or  else  a  framework  and  sheeting 
of  timber.  The  principal  gallery  immediately  behind  the 
Counterscarp  wall,  is  termed  the  counterscarp  or  magistral 
A  ry.  An  <  nvt  loping  gall*  ry  is  one  parallel  to  the  counterscarp 
gallery,  and  at  some  ::"  or  1"  yards  in  adva 
galleries  leading  outward  from  the  counterscarp  gallery  are 

The  galleries  which   com 
eral  listening  gallerii 

uticular  name-  from  tin  ir  size,  as  the 


-•"'-  MIXES. 

dual  or  grand  galleriet,  which  are  6  feet  high  and  <'»  feet  wide. 
( ommon  galL  /•/<*,  ••       0       "  "3 

ffalfgalltries,  "       U     "  «    3        " 

Branch    .  "       3£     "  "    2£      " 

Small  Branetiuj  "      >J\     *          "    2        " 

730...Expeeimewm.  But  little  advance  by  experiment  has 
been  made  in  the  subject  of  mines,  owing  to  the  time,  labor 
and  expense,  which  a  prosecution  of  the  subject  demands ;  and 
the  practice  has,  therefore,  undergone  but  slight  changes  sinoe 
the  earliest  introduction  of  thia  means  of  attack  and  defence. 
The  following  facts,  drawn  from  observation,  comprise  almost 
all  that  is  at  present  known  on  the  subject: 

1st.  Jn  solid  rock,  an  explosion  causes  the  rock  to  split  in 
Various  directions,  and  it'  the  charge  is  heavy,  will  break  it 
into  small  fragments,  which  are  frequently  thrown  to  a  great 
distance. 

2d.  In  sand,  the  gazes  seem  to  penetrate  between  the  grains, 
producing  a  crater  of  a  regular  form,  the  radius  of  the  appei 
circle  of  which  is  generally  small  in  comparison  with  the 
depth.     I 

3d.  In  ordinary  tenacious  soils,  the  first  effect  of  the  explo- 
sion is  to  produce  a  rumbling  noise,  and  a  sensible  trembling 
of  the  earth  around  the  mine  to  a  Considerable  distance;  the 
ground  directly  over  the  mine  is  next  observed  to  rise  in  the 
form  of  a  spherical  segment,  which  increases  perceptibly  until 
the  smoke' commences  to  issue  forth  around  its  base;  the  ex- 
plosion outward  follows  immediately  on  this  last  change,  the 
earth,  mingled  with  smoke  and  dame,  being  thrown  upward 
and  outward,  so  as  to  assume  a  form  something  like  a  water- 
spout ;  part  of  the  earth  falling  back  into  the  crater  and  apart 
without,  forming  a  ridge  around  its  mouth. 

The  two  most  remarkable  features  of  the  explosion  are  its 
internal  and  external  effects;  the  first  producing  the  crater, 
the  second  so  disturbing  the  earth  for  a  considerable  distance 
around  the  crater  as  to  till  up  cavities,  destroy   galleries,   etc., 


min  258 

•within  the  sphere  of  its  action;  these  effects  extending  farther 

in  a  lateral  than  in  a  downward  direction. 

The  charges  and  their  effects  do  not  follow  the  same  ratio, 
the  last  increasing  less  rapidly  than  the  first.  Experiment  has 
shown  that  the  charges  may  even  be  increased  one  or  two 
pounds  per  4  cubic  yards,  without  increasing  the  crater  radius; 
the  only  effect  of  this  increase  of  charge  being  to  throw  more 
of  the  earth  clear  of  the  crater. 

Prom  experiments  made  on  common  mines,  with  a  line  of 
Least  resistance  not  exceeding  l.~>  feet,  it  has  been  ascertained 
that  the  tenacity  of  the  earth  is  completely  destroyed  around 
the  crater,  to  a  distance  equal  to  the  line  of  least  resistance, 
and  that  empty  galleries  are  broken  in  at  a  distance  of. 
and  a  halt*  the  same  line. 

In  homogeneous  soils,  the  resistance  due  to  the  tenacity  of 
the  soil  is  nearly  proportional  to  the  mass. 

It  was  lor  a  long  time  supposed  by  miners  that  a  crater  could 
not  be  formed  with  a  diameter  greater  than  twice  the  line  of 
least  resistance,  with  any  eharjge;  but  the  experiments  of  Be- 
lidor  have  shown  that,  by  successive  augmentations  of  the 
charge,  tin-  crater  radius  may  be  increased  to  six  times  this 
line,  but  not  much  beyond  ;  that  within  this  limit  tin-  ratio 
the    diameter-   of  the    craters  is  nearly  that  of  the  square  POOl 

of  the  charges;  and  that  galleries  ean  be  destroyed  by  such 
mines  at  distances  of  four  times  their  line  of  hast  resistai 
[....Theory.     The  physico-mathematica]  theory  of  mil 
11  \i-ry  imperfect,  owing  to  the  impracticability  of  a» 
taining  the  exact  effects  of  the   explosion   of   powder   in   a 
medium  which   is  seldom  ho  and  the  i 

which,  arising  from  it.-  tenacity,  con 

:i  of  tie  only  be  arrived  at   by  a  ->\ 

experiments  made  with  mini, 
■in  the  lementary  «i.  formula 

■  nt   in   ns-  .  nine  the  charges  for 

mpirical,  and  their  n  - 
only  within  the  limits   in   which  the} 


254  mi\ 

meats.  For  most  cases  in  practice,  these  approximations,  are 
near  enough,  and  valuable  as  the  only  guides  that  the  mine* 
has  to  refer  to. 

^32... The  resistances  which  the  gazes  overcome  are  the  weight 
of  the  volume  of  earth  thrown  from  the  crater,  the  tenacity  of 
tin-  medium,  and  the  atmospheric  pressure  od  the  upper  circle 
of  the  crater.  The  two  firsl  are  proportional  to  the  ma- 
earth  thrown  out.  and  the  last  to  the  upper  surface  of  the 
crater.  To  express  the  ratio  of  these  resistances  to  the  char 
let  us  represent  in  any  two  mines  by 

c  d,  the  charges; 

/•  /•'.  the  radii  of  the  craters; 

1 1\  the  lines  of  least  resistance; 

d  d\  the  weight  of  the  unit  of  volume  of  the  two  soils; 

it  n',  the  constants,  which,  multiplied  into  the  weights,  will 
express  the  tenacities; 

h  //,  the  heights  of  the  atmospheric  columns  reduced  to  the 

densities  a&  the  .-oils. 

Whatever  may  be  the  form  of  the  crater,  its  volume  can  he 
expressed  in  terms  of  the  surface  of  the  upper  circle,  and 
some  fractional  part  of  the  line  of  lea>r  resistance  ;  bo  that 
if  we  represent  by  1  I  and  J.  I'  this  fractional  part  of  the  line 

of  least  resistance  in  the  two  cases,  we  shall  have  for  the 
expression  of  the  two  volumes: 

7rr2x  Land«V*X  '' ; 

m 

and  for  their  respective  weights, 

!!>2'x  <1,  and77r''2.''  x  d ; 

m  in' 

to  express  the  tenacities  we  have, 

a  2 

~r  _*ji, and£r!  ld'x  n': 

vi  m' 

and  for  the  weights  corresponding  to  the  atmospheric  pressures, 

nr-/<  <%  and  *?'*'&  &. 
From  these  expressions  we  obtain  the  proportions 

c  :  d  : :  0[(»  +  l)  I  +  m  //]  :  tl*  [(n'+l)  +1'  m'hf\ 


mini  -.  255 

For  the  same  soil,  as  m=7n',  ??  —  »',  d=d',  and  h  =  h',  tin's  pro- 
portion becomes 

c :  c".  -y-(i+^h)  :  ^(r+i"iA'). 

733. ..The  relation  between  any  two  charges  of  mines  in  the 
same  soil,  expressed  by  this  proportion  gives  the  means  of  ob- 
taining the  charge  for  any  crater  when,  by  experiment,  the 
crater  formed  by  any  known  charge  has  been  found,  provided 
the  quantities  n  and  //  are  known.  Of  the  first,  nothing  defi- 
nite is  known  but  that  it  varies  with  the  kind  of  soil.  The 
rod  lias  beet)  assumed  equal  to  11  feet.  This  want  of  defi- 
niteness  in  the  value  of  these  quantities  has  led  to  omitting 
them  in  the  proportion,  when  used  for  practical  purposes,  in 
which  case  it  takes  the  felTowmg  form  : 

'[  \ :  i  r  '* :  v  ¥  *. 

T\\\>  is  termed  the  Mint  r*a  Ride,  as  it  is  used  for  calculating 
tahles  of  charges  for  different  soils  ;  and  its  results  do  not  differ 
materially  from  those  of  experiments* 
Making  l=l\  the  proportion  becomes 
c  .  c  .  .r2  .  r  *, 
a  proportion  also  differing  but  little  from  the  results  obtained 
within  the  ordinary  Limits  of  practice,  when  the  lines  of  least 
me  for  different  chargi 
734...Assumjng,  as  is  the  case  in  common  mines,  that  the 
craters  are  similar  solids,  then  I  ',  $',  \r  '.  r  ;  hence, 

•  :  /' 
another  form  of  the  H  -■  d    in  calcu- 

lating the  tables  of  cl  >r  similar  mrni 

The  manner  in  which  this  rule  is  applied  to  calculate  cl 
omtnon  mine*  the  quantity  of  powder,  y.  in 

pounds,  required  to  throw  up  one  cubic  ys 

mud  by  experiment.     As  the  solid  a  trun- 

ial    to  1  ]■>'>  /   .  ;  the  Hi,, 

.  the  i  olum<   of  tl  line  of  L 

ird,  will   be    :  ,,r 


256  minis. 

11-6;  this  volnfne,  multiplied  by  q,  will  give  the  charge  in 

pounds  for  this  crater,  but  from  the  proportion  e  \  <■' ;  ;/:;  '.  ('3, 
there  obtains : 

c:  n-6  y  ::/•'*:  i  :;.  orc=li-6?Z8, 

for  the  charge  for  a  crater'whose  line  of  least  resistance  is  I. 

'  ,7  M,  chargt ,  M-  r^/bn  ./"/■  a  .</''''.  h  K/n  of  least  resista 
cul„  this  line,  expressed  in  yards  }  tah   ll-6>of  tin  result  and 
multiply  it  by  the  number  of  pounds  required  to  throw  out  a 
cubic  yard  of  tJu  soil  in  Question. 

The  following  table  expresses  the  values  of  g  : 

Lb*.      Oz. 

Light  sandy  earth 1  13 

Hard  sand 2  00 

Common  earth 1  10 

Wet  sand 2  2 

Earth  mixed  with  pebbles 2  8 

Clay  mixed  with  loam 2  8 

Eock 3  10 

735. ..As  the  Miner's  "Rule  is  applicable  only  to  common 
mines,  resort  must  be  had  to  some  other  to  And  the  charges  for 
overcharged  and  Undercharged  mines.  The  formula  in  most 
general  use  for  these  cases  are  those  of  Lebrun,  a  French  engi- 
neer; which,  although  not  based  on  any  satisfactory  hypothesis, 
nevertheless,  coincide  nearly  in  their  results  with  those  ob- 
tained by  experiments  within  ordinary  limits.  The  hypothesis" 
assumed  to  obtain  these  formula  is  as  follows:  Suppose  two 
craters,  formed  by  two  different  charges,  o  and  <■',  with  the  same 
line  of  least  resistance,  one  giving  a  crater  radius,  ;•,  equal  to  the 
line  of  least  resistance}  the  other  a  crater  radius,  Ji,  greater, 
the  difference  of  the  radii  being  R — r.  Next,  suppose  the 
charge  6  to  belong  to  a  common  mine,  of  which  the  crater  ra- 
dius is  r  •  r — /',  being  the  difference  of  the  radii  of  two  craters 
of  the  common  mines  of  which  the  charges  art'  o  and  <■' ;  then 
the  ratio  of  the  two  differences  here  expressed,  arising  from 
the  same  increase,  c'}  of  the  charge  c,  will   be  constant  under 


MINT-.  857 

all  circumstances  of  variation  of  soil,  and  of  the  lines  of  Least 
resistance.     Calling  /f  this  constant  ratio,  there  obtains: 

}i—r_  t-#  • 

r'  —  r—  h  ' 

assuming  R=n  r,  this  formula  becomes 

r(n— 1)    _  jy-  , 
r' r    —  IX  ) 

<<=;.x(ra— i)+i; 

but  as  f  and  r  belong  to  similar  craters,  the  "Miner's  Rule 

3 

gives   c=  — :  from  this  there  obtain-. 

The  quantity,  h".  which  enters  into  this  expression1  must  be 
ascertained  by  experiment,  as  indicated  by  the  process  fol- 
lowed in  obtaining  the  formula.  From  a  comparison  of  a 
number  of  experiments,  the  value  of  h' isr 
*=c[6.91  n+0.09}*. 
i36...The  preceding  method  is  also  applied  to  find  a  formula 
for  the  charges  of  undercharged  mines.  In  this  ease,  R  and 
/■'    being   supposed    less    than    /',  L~~~^jr    and    hence   c'— 

The  constant  K  in  this  case,  ia  determined  from  a  result  of 
experiment;  that  if  a  certain  charge  of  powder  forms  a  com- 
mon crater  with  a  Line  of  least  resistance  I,  the  same  charge 
will  not  produce  any  external  effect  when  the.  line  of  I 

i  to   1|  /  or  7-4  /  .•  and,  i  'ally,  if  a 

charge  produce!  no  external  effect  with  a  line  of  leasl 

/.  the  same  charge  will  form  a  common  mine  under  a  line 
of  !  1-7  /.     If.  then,  the  charge  </,  by  sup] 

tion.  ■•  product  sternal  effect   under  the  lint 

Leasi  .  it  will  prod  'Ninon  mine  under  a  line 

of  l  from  this,  by  the  M 

ibstituting    this  value  ol   •  ■'  in   1  f),  and 

33 


258  MINES. 

■),=,,.  its   corresponding  value  for  this  of  <■' :  there   obtains 

•^=-^-,  which  result,  substituted   in   the  same   Eq.  (Jf)  it   then 

'becomes  </=c  [l— *(1— ft)]3;    hence  </=c  ('""7M)\  which    is 

the  formula  for  undercharged  mines.  • 

737...(t.\i.i.i  kv  Fkamks.  Temporary  galleries  arc  made  of 
framework  covered  in  by  plank,  and  are  prepared  but  a  short 
period  before  they  are  required  for  pise, 

738.. .Tin'  frames  of  temporary  galleries  consist  of  four 
pieces:  two  uprights  termed  stanchions,  and  two  horizontal 
pieces,  the  one  at  top  termed  a  hap  *///.  and  the  bottom  piece 
a  ground  sill}  PI.  8,  Fig.  A,  shows  the  connection  between 
the  parts  of  the  frame. 

The  plank  or  boards  which  cover,  in  the  frames  are  termed 
s fleeting.  The  top  sheeting  of  the  frames  usually  consists  of 
boards  from  3  feet  6  inches  to  4  feet  in  length,  from  7  to  12 
inches  in  width,  and  from  1  to  1-|  inches  thick.  The  side 
sheeting  may  have  the  same  length  and  breadth,  but  need  not 
be  thicker  than  from  £  to  1  inch.  To  set  the  frames  up  and 
retain  them  in  their  places,  slips  of  plank  termed  battens  are 
used,  which  are  about  2£  inches  wide  and  1  inch  thick. 

The  frames  may  be  either  of  well  seasoned  oak  or  pine,  the 
latter  is  preferable  as  lightest.  The  parts  of  each  frame  re- 
ceive the  dimensions  in  the  annexed  table: 


Common  gallery, 

iu     Bin      u      y^T       j,     sin 

6X4, 

5X-r), 

6X6. 

Half  gallery, 

■n_xH, 

"        4*XU, 

&X4*. 

Branches, 

3$X3, 

"        34X3*. 

'      HXH, 

Small  branches, 

8X8, 

3X3. 

4X3, 

739. ..Sua i  r  Frames*  PI.  8,  Figs.  3,  4,  5.  A  shaft  is  a  ver- 
tical pit,  lined  with  sheeting  on  the  outside  of  frames  which 
are  placed  horizontally,  and  at  suitable  intervals  apart. 

The  cross  sections  of  shafts  are  either  squares  or  rectangles; 
the  dimensions  of  the  sides  of  the  section  depending  on  the 
object  of  the  shaft.  When  this  is  for  driving  a  gallery  from 
the  bottom  of  the  shaft,  the  dimensions  of  the  shaft  frames,  in 


MINI  B.  259 

the  clear,  must  be  at  least  equal  to  that  of  the  gallery,  from 
out  to  out  of  its  sheeting.  A  shaft,  sunk  for  establishing  a 
mine  chamber  simply,  should  usually  he  of  the  least  dimen- 
sions, which,  to  allow  the  miner  to  work  with  facility,  must 
not  he  less  than  8  feel  1>\   -  feet  in  the  clear. 

Two  kinds  of  frames  are  usually  requisite  in  sinking  shafts: 
a  tojifrniin,  Fig.  1,  formed  of  four  pieces,  halved  to  fit  each 
other,  which,  when  put  together,  have  the  same  dimensions  in 
the  clear  as  the  shaft,  each  piece  projecting  beyond  the  side, 
or  having  an  over  length  of  1£  to  2  feet;  the  other  is  termed 
a  sid<?  frani<\  Fig.  2,  and,  also,  consists  of  four  pieces  of  smaller 
scantling  than  the  top  frame,  halved  at  the  ends  to  lit,  its  di- 
mensions in  the  clear  being  the  same  as  the  other. 

In  very  loose  soil  it  may  he  necessary  to  use  a  temporary 
frame.  <<.  Fig.  1.  termed  an  auailiary  fram\e.  This  is  some- 
what Larger  in  the  clear  than  the  preceding.  Its  uses  will  he 
explained  farther  on. 

The  opposite  pieces  of  each  frame  arc  marked  with  a  saw 
out,  termed  a  More,  at  their  middle,  on  the  upper  side.  The 
scores  serve  to  fix  the  position  which  the  frame  should  occupy 
when  laid. 

The  scantling  for  top  frames  is  usually  6  inches  square;  that 
de  and  auxiliary  frames  4.^  inches,  for  a  shaft  over  A\ 
in  the  clear.     For  smaller   shaft.-,  the   scantling   may  he  of 
smaller  dimensions. 

740.. .Shaft  Inn  kval.  The  term  interval,  hoth  in  shafts 
and   galleries,  expresses  the   distance   between    two  adja 

frames  added  to   the    thickness   of  the    scantling   of  tie 
measured  in  the  direction  of  the  axis  of  the    shaft.  ■  tc.      With 
tling  and   sheeting  of  the   usual  dimensions,  the   interval 
should  not  he  greater  than  '.)$  I 

Pbob.,  Fig.  3.     Tht    depth   qf  a  shafts  and  ih>    height  ■ 
gallery  1<>  lead  from    tlu    bottom    of  tfu   shaft,  being* 

d. 
A «i'l  tog  I  lier  the  In  top 

of  it-  ground  sill,  tiie  thickness  of  tie 


260  MINES. 

thickness  <>f  the  shaft  frame;  t<>  this  sum  add  2  inches  for  free 
space  between  the  gallery  frame  and  the  shaft  frame  next 
above  it,  t<»  introduce  the  top  Bheeting.  Subtract  this  sum 
from  the  depth  of  the  shaft,  and  divide  the  remainder  into 
any  convenient  number  of  equal  or  unequal  intervals,  each 
not  greater  than  8|  feet. 

Lei  the  depth  of  the  shaft,  for  example,  be  22  feet,  and  the 
height  of  the  gallery  -!'<;".    Then: 

From  ground  sill  to  exterior  of  top  sill t 4M1" 

Top  sheeting 0.1 

Shaft  frame 0.4* 

Free  space D.2 

Total 5.6* 

This  taken  from  22  feet  leaves  1G'.5£",  which  can  be  divided 
into  four  intervals  of  3'.4"  each,  leaving  cue  interval  of  3'.  14/', 
which  may  be  placed  either  at  top  or  bottom,  but  best  in  the 
latter  position. 

'^...Construction  of  Shut.  To  construct  the  foregoing 
shaft  in  a  loose  soil,  there  will  be  required  a  top  frame;  live 
side  frames  for  Hie  intervals  above  estimated ;  two  for  the  re* 
maining  lower  portion  of  the  Bhaft;  one  auxiliary  frame;  four 
battens  for  each  interval  of  the  length  of  the  interval  added  to 
the  thickness  of  the  shaft  frame;  from  12  to  20  Bquare  pickets 
about  18"  long ;  with  the  machinery  and  mining  tools  requisite 
for  the  operation. 

71-.. .The  work  is  laid  out  by  driving  a  pickel  to  mark  the 
axis  of  the  Bhaft,  and  two  others,  which  with  the  first  are  in 
the  vertical  plane  containing  the  axis  of  the  gallery.  A  level 
bed  is  then  made  for  the  top  frame,  the  pieces  of  which  are 
accurately  laid  and  confined  by  pickets,  one  at  the  end  of  each 
piece;  care  being  had  to  drive  the  two  pickets  of  each  piece 
together,  so  ihat  its  true  position  may  be  kept,  other  pick 
may  be  driven  temporarily  on  the  outside  of  the  frame,  a1  the 
angular  points'  After  the  frame  is  laid,  the  accuracy  of  its 
position  is  tested  by  seeing  whether  the  distances   from   the 


MP-  L'l'.l 

centre  of  the  central  picket  to  the  interior  angular-  points,  "f, 
in  other  words)  the  semi-diagonals^  are  equal :  if  they  are,  the 
position  is  correct. 

M8... The  excavation  is  now  commenced,  and,  if  the  crumb- 
1  i 1 1 ir  of  the  soil  does  not  interfere,  may  be  carried  as  far  as  the 
position  of  the  first  side  frame;  the  sheeting  boards,  inserted 
between  the  soil  and  the  exterior  of  the  top  frame,  being 
gradually  advanced  with  the  excavation  ;  here  the  first  side 
frame  is  hung  by  four  battens,  two  being  nailed  to  each  j 
of  the  opposite  Bides  >>(  the  top  frame  and  to  the  two  com  s- 
ponding  pieces  of  the  side  frame,  the  halvings  of  which  are 
turned  upward  :  after  these  pieces  are  adjusted  by  their  score! 
and  fixed,  the  other  two  pieces  are  laid  on  them,  the  halvings 
down,  and  secured  by  nails. 

71  I. ..This  frame  being  fixed,  the  ends  of  the  Bh(  eting  of  the 

next  interval  may  be  inserted  between  it  and  the  sheetil 
the  tir.-t  interval,  and  the  excavation  continued.  The  soil  qow 
becoaung  troubli  some  by  it>  crumbling,  measures  must  he 
taken  to  retain  it  firmly  until  the  second  frame  i>  laid. 
this  purpose  the  auxiliary  frame.  Fig.  1.  is  introduced,  ami 
hung  midway  in  the  interval,  like  the  usual  frame.-.  The 
■  ting  which  thus  far  ha-  been  gradually  advtmced  with  the 
ivation,  inclined  outward  at   bottom,  to  gain  room 

for  the  auxiliary  frame,  by  wedges  inserted  between  the  boards 

the  two  intervals.      After   the  auxiliary  frame  is   fixed,   the 
ivation   and   sh«  i  carried   on   to  the  bottom  ol 

interval,  the  next   frame  hung,  and  the 'sheeting  for  the 
«  interval  introduced.     The  auxiliary  fram<  and 

placed  in  the  mxt  position,   when   r<  ached  by  th< 
work  will  proceed  in  this  order  until  the  - 
ted;  wh<  iven  in  the  bottom,  I 

mark  the  central  point. 

i;k.      A    sketch,    made  to  a  suita1 
hand  for  in 

more    particularly  m-ce^ary  for  trull  cry  w 
for  which  diould   b< 


numbered,  as  they  serve  not  only  for  reference  to  guide  tho 
miner,  hut  to  determine  positions  and  dimensions  <»t'  some  of 
the  important  portions. 

745... Combinations  of  Timber  Q  lllebibs.  A  gallery  which 
leads  from  another  is  termed  a  return,  and  is  called  obltqtn  <>r 

Idngular,  according  to  whether  the  projections  of  the  axes; 
of  the  two  galleries  make  a  right  or  an  acuU  angle.  The  gal- 
lery  from  which  the  return  is  made  is  termed  a  gallery  of  de- 
parture. When  the  floor  of  the  return  rises  or  falls  from  that 
of  the  departure,  the  return  gallery  is  termed  ascending  or 
d*  8d  nding. 

7  1»''...VTmi:ki.\<,  Plans.  To  make  a  working  sketch  of  a 
combination  of  galleries,  the  projections  of  the  axes  are  first 
laid  out;  their  points  of  intersection  marked;  and  the  dis- 
tances and  reference  between  all  the  points  written.  The  half 
width  of  each  gallery  in  the  clear  being  next  set  off  on  each 
side  of  its  axis,  a  line  is  drawn  for  it,  then  one  parallel  and 
exterior  to  it  at  the  thickness  of  the  gallery  frame,  and,  finally, 
a  second  to  mark  the  exterior  line  of  the  sheeting. 

The  line  0  I),  Figs.  G,  7,  8,  is  the  axis  of  the  gallery  of 
departure,  and  .1  I>  that  of  the  return.  The  line  a  b  is  the 
interior  line  of  the  gallery  frames;  o  d  the  exterior  line  of  the 
same  ;  e  f  that  of  the  sheeting.  The  corresponding  Lines  for 
the  remaining  half  of  the  gallery  of  departure,  and  those  of 
the  return,  will  he  readily  recognized.  The  frames  in  and  ///' 
bound  the  entrances  to  the  returns;  and  those,  //,>',  of  the 
auxiliary  return,  the  entrance  to  the  oblique  return,  Fig.  8. 

The  ease  of  a  change  of  direction  in  a  gallery  is  shown  in 
Fig.  '•'•  Here,  to  obtain  room  for  the  miner  to  handle  the 
sheeting,  etc..  an  end  of  an  auxiliary  gallery  is  made  oil',  on 
the  salient  angle  of  the  break,  just  large  enough  for  the  object 
in  view.  Having  set  off  these  lines,  the  points  of  intersection 
of  the  exterior  lines  of  the  sheeting  of  the  return  v\ilh  the 
exterior  ami  interior  lines   oC  the    frame   of  the    gallery   of  de- 

parture,  are  marked  as  follows,  to  determine  the  distance  to 

be  left   between   the.  two   frames  of  the  gallery  of  departure, 


MIXER.  263 

between  which  the  entrance  to  the  return  is  placed:  1st.  when 
the  projections  oi  the  axes  make  a  right  angle,  then  the  inter- 
sections  of  the  exterior  lines  of  the  sheeting  with  the  Interior 
lines  of  the  framed  are  marked  :  the  entrance  to  the  return 
will  lie  equal  to  the  distance  between  the  exterior  lines  of  the 
sheeting  of  the  return  :  2d,  when  the  angle  ie  between  45° 
and  90°,  the  intersection,  0,  of  the  exterior  line  of  the  sh 
ing  of  the  return,  which  lies  within  the  angle  formed  by  the 
axes,  with  the  exterior  line,  c  d,  of  the  gallery  frames,  and 
that,  o',  of  the  other  exterior  line  of  the  sheeting  with  the 
interior  line  of  the  same  frames  being  marked,   will   give   the 

points  between  which  the  frames  of  the  gallery  of  departure 
must  he  placed  to  form  the  entrance;  3d,  when  the  angle  be- 
tween the  a  --than  4.">:,  the  frame.-  bounding  the  en- 
trance to  the  return  would  fall  too  far  asunder.  It  will,  there- 
fore, he  requisite  to  make  a  rectangular  auxiliary  return  from 
the  gallery  of  departure,  into  which  the  oblique  return  will 
have  it>  entrance.  To  determine  the  position  of  the  rectangu- 
lar return.  Fig.  8,  a  line,  r  »,  is  first  drawn  exterior  to  the 
sheeting  of  the  gallery  of  departure,  and  at  a  distance  from  it 
equal  to  the  thickness  of  the  frames  to  he  aged  for  the  aux- 
iliary return;  the  intersection,  »,  of  the  exterior  line  of  the 
ting,  which  lies  within  the  angle  of  the  axes  and  the  last 
line  drawn,  being  marked,  will  give  the  point  through  which 
the  inner  line  of  the  frame-  of  the  auxiliary  return  i.-  to  ]„. 
drawn.  This  line  being  determined,  all  the  other  line-  for 
this  return  can  he  readily  Bet  out.'  The  re.-t  of  the  problem 
will  he  treated  as  in  the  second  CI 

V  17  . J^i  v  \i  i  -.      From  an  examination    of  the    ab< 
it  will  be  seen  that  tl  t  to  be  accomplished  is  so  to] 

the  two  frame-  .,('  the  gallery   of  departure,   which    bound 

entrance  to  the  return,  that  the  itanchii 

11    not  he  in  the  w  ay  of  the   miner    wl  • 

;  or,  in  other  words,  if  the  petui  .  boi 

that   could  he  pn  1,  like  a  dra 


264  min 

of  its  axi>.  tlic  stanchions  in  question  should  not  hinder  this 
movement. 

reral  other  problems,  of  a  like  character,  may  present 
themselves  in  returns,  and  in  changes  of  direction  in  galleries, 
which  it  will  be  unnecessary  to  treat  here,  a>  the  illustrations 
above  given  will  readily  suggest  the  methods  to  be  adopted 
for  their  solution. 

T48...1  >i  i  i:i:mi\  \ti..\  of  <  S  \u.i  i:v  A  kes.  Saving  set  off  all 
the  lines  on  the  working  sketch,  and  marked  the  positions  of 
the  different  frames,  etc.,  at  the  junctions  of  the  galleries,  their 
forms,  dimensions,  and  also  their  .exact  positions  with  respect 
to  any  diced  point,  can  be  accurately  determined  from  the 
scale  of  the  sketch,  and  be  written  upon  it  for  reference  in 
conducting  the  work.  .  For  example:  in  Fig.  7,  the  determi- 
nation of  the  points  o  and  o',  fix  the  positions  of  the  gallery 
frames  ///  and  ///,  and  the  form,  position  and  dimensions  ot 
the  oblique  frame  q,  of  the  return,  where  the  galleries  join. 
Having  set  off  these  parts,  the  point  /,  on  the  axis  of  the  gallery 
of  departure,  equidistant  from  the  points  k  and  /,  ot'  the  frame 
y.  can  be  determined.  .This  point,  marked  by  a  picket,  serves 
to  fix  these  points,  and,  with  the  picket  at  F,  the  direction  of 
J    B. 

749... Landings.  The  portion  of  the  floor  of  the  gallery  be- 
tween the  frames  that  bound  the  entrance  to  a  return,  is 
termed  a  landing,  as,  for  example,  the  spaces  between  the 
frames  m,  m',  and  u\  v.  The  landing  is  in  all  cases  horizontal, 
as  well  as  that  portion  of  an  oblique  return  between  the  oblique 
frame  y,  and  the  one,  a?,  n « ■  x t  succeeding,  which  last  should 
not  be  placed  farther  than  an  ordinary  interval  from  the  farth- 
est point  of  y. 

7:.M...(iAi.i.i  i;v  Ivii  i:\ai.s.  Having  determined,  by  means 
of  the  working  sketch,  the  landings  and  their  frames  with 
respect  to  the  points  of  intersection  of  the  axis  of  the  gallery 
of  departure  with  those  of  the  returns,  the  intervals  of  this 
gallery  can  be  calculated,  and  their  positions  marked  out  on 


iron  z65 

the  sketch.    The  manner  of  making  this  estimate  will  be  I 
illustrated  by  the  following  example: 

Let  .1  B—118  feet,  Fig.  1".  be  the  total  length  of  a  galleay 
of  departure,  estimated  horizontally  along  its  axis,  from  tne 
central  picket  of  the  shaft  from  which  the  gallery  starts.  At 
the  point  6",  44  feet  from  A,  the  axis  of  a  rectangular  return 
commences,  and  at  I),  44  feet  farther,  that  of  an  oblique  one. 
The  part  A  C of  the  gallery,  Fig.  11,  is  to  l»e  a  common  great 
gallery;  the  part  C  D,  Fig.  12,  a  common  gallery;  and  the 
part  />  />'.  Fig.  13,  a  great  branch.  With  these  data,  it  is  re- 
quired to  determine  the  intervals  for  the  different  portions  of 
the  gallery. 

To  find  the  interval  for  the  first  portion,  A  C,  subtract  from 
the  total  distance,  41  feet,  tin-  following  aggregate: 

Half  the  width  of  the  shaft  in  the  clear 2'.2" 

The  thick  ne--  ,.('  1  lie  In  west   shaft    frame <».  l.V 

Half  the  width  of  the  landing  at  C 8.6f 

The  thickness  "fa  gallery  frame  at  the  landing 0.5 

5'.0" 
which   leaves  -'-1   feet   to  he   divided    into  Bnitable   intervals, 
which  may  he  done  by  making   twelve  of  them   each    .".  f. 
inch 

The  intervals  of  the  portion  C  I>.  will  he  found  as  follow.-,: 
From  44  feet  take  the  following  sum: 

half  the  width  of  the  landing  at  (' l>'ji$" 

Thickness  of  the  landing  frame 0.5 

The  distance  from  I>  (as  found  from  the 

landing  frame  beyond    0.9 

Thickness  of  gallery  frame  at  landing  If 


which  leaves  10  fe<  I  5  in<  1  i  -.  T  ij  can  he  divid  nine 

intervals,  i  ach  8'.  l  .  and  fonr  sen. 

ml  the  intervals  for  I  '     • 

fellowing  ite: 


266  mhi 

Distance  from  />  to  frame  of  landing  beyond  it 4'.5" 

Thickness  of  landing  frame  beyond  1) 0 

Thickness  of  Last  frame  at  li Q  .-.I 

This  leaves  25  feet,  which  can  be  divided  into  six  intervals  of 
:;'.!'"  each,  and  two  of  3'. 

751...Slope-Block.  In  Betting  the  ground  sills  of  frames  in 
ascending  <>r  descending  galleries,  a  small  cubical  block  <>( 
wood,  termed  a  slope-block,  is  nsed.  This  is  a  cubical  block, 
the  edge  of  which  is  equal  to  the  difference  of  level  between 
the  ground  sills  of  an  interval.  To  determine  the  height  of 
the  slope-block  for  any  portion  of  a  gallery  where  the  intervals 
are  equal,  or  nearly  so,  the  difference  of  level  or  of  refer* 
of  the  two  extremities  of  the  portion  must  be  divided  by  the 
number  of  intervals.  Thus,  in  the  portion  of  the  gallery  from 
A  to  6',  Fig.  10,  there  is  an  ascent  of  5',  or  60",  and  twelve 
intervals;  the  edge  of  the  slope-block  will,  therefore,  he  60- 
lii"  =  r/.  In  the  portion  from  C  to  J>.  there  is  a  fall  of  ■!'.  1". 
or  40",  and  thirteen  nearly  equal  intervals;  the  edge  of  the 
slope-block  will,  therefore,  be  3". 7,  nearly. 

752. ..Ai  \ii.iAi:v  Frames.  In  loose  soils,  besides  the  ordi- 
nary gallery  frames,  there  is  required,  as  for  shafts  in  the 
same  soil-,  an  auxiliary  gallery  frame.  This  frame,  Fig.  14,  0, 
Fig.  15,  is  somewhat  wider  than  an  ordinary  gallery  frame, 
and  somewhat  lower  than  it.  Its  cap  sill  is  rounded  on  top, 
and  has  two  mortices  on  its  lower  side,  to  receive  the  tenons 
with  which  the  two  stanchions  are  finished.  The  mortices  are 
a  little  longer  than  the  tenons — the  latter  being  confined  in 
them  by  wedges  when  the  frame  is  set  up.  To  adjust  the 
frame  when  set  up,  a  pair  of  folding  wedges  are  placed  under 
each  end  of  its  ground  sill.  By  these  various  contrivances, 
the  frame  can  he  readily  set  up  or  taken  apart. 

753...CoNsTi:rcno.N  of  (  Jai.i.i- ,i:ii:s.  To  explain,  now,  the 
practical  operations  in  driving  a  gallery,  let  an  example  be 
taken  where  the  soil  is  loose,  and  the  floor  of  the  gallery  rises 


min  2G7 

from  the  point  of  departure.  In  this  case,  the  first  frame  of 
the  gallery  0,  Fig.  16,  must  be  set  up  within  the  shaft  and 
against  the  shaft  frames,  <>n  the  side  from  which  the  gallery  is 
to  open.  The  ground  sill  of  this  frame  being  laid,  the  stan- 
chions are  secured  to  the  intermediate  shafi  frames  of  the  last 
interval  by  battens,  and  the  top  sill  fastened.  A  horizontal 
beam,  <\  is  then  secured  to  the  under  side  of  the  top  shaft 
frame  of  the  same  interval,  to  preserve  the  proper  slope  for 
the  top  Bheeting  when  inserted,  wedges  being  placed  between 
this  beam  and  the  sheeting  hoard  for  this  object.  A  like 
arrangement  for  the  side  sheeting  may  be  made  it'  necessary. 
The  excavation  of  the  gallery  is  now  commenced  at  top,  by 
forcing  down  with  a  crowbar  the  sheeting  of  the  shaft,  on  the 
side  of  the  gallery.  The  earth  i>  removed  gradually  forward 
and  downward,  and  the  gallery  sheeting  advanced  at  the  same 
rate.  When  the  excavation  has  reached  as  low  as  the  inter- 
mediate bIi aft  frame,  the  piece  of  it  that  sustains  the  lower 
portion  of  the  sheeting  i>  removed,  to  allow  the  excavation  to 
proceed.  When,  in  this  way.  the  earth  is  removed  as  far  as 
the  middle  of  the  first  interval,  the  auxiliary  gallery  frame, 
•  11]..  to  support  the  top  and  side  sheeting  until 
the  second  gallery  frame  is  placed.  To  place  this  last  frame, 
the  position  of  the  ground  sill  i.-  first  determined.  Fig.  17,  by 
placing  the  slope-block,  0,  on  the  ground  sill  first  laid,  ami 
then,  by  a  common  masoi  '.  .1,  upon   the  side  of  wtiich 

the  interval  i>  marked,  laid  upon  the  slope-block,  bringing  the 
top  of  the  ground  >ill  on  the  same  level  as  that  <>!'  t. 
block.     The  sill  l>cim_r  adjusted  and  firmly  .-  mu- 

cinous are  next  set  up,  a:.  I  by  battens  to  the  stanch 

of  the  first  frame,  and  th 

The  adjustments  of  the   Btanchio  are  made  hy 

an  ordinary  plumb-line,  by  1  which  1 

■ 
and  ground  sills  brou^  ical  plai 

the  gallery. 
The  battel  illy.     In  a 


2G8  MiN 

are  nailed,  alternately,  at  4  and  v  inches  below  tbe  cap  >\\\. 
In  others,  Fig.  L7,  they  are  nailed  I  incbes  below  Ihe  lowe* 
of  the  cap  sills  of  the  two  frames  which  they  unite;  this  will 
bring  them  at  4  inches,  added  to  the  height  of  the  slope-block, 
below  the  ot"her. 

The  auxiliary  frame  is  not  taken  down  until  wedges  have 
beeil  placed  between  the  sheeting  and  the  frame  last  placed, 
in  order  to  introduce  the  boards  for  the  next  interval ;  and 
these  last  are  kept  in  the  proper  direction,  as  the  excavation 
is  advanced,  by  wedges  inserted  between  them  and  the  sheet- 
ing of  the  interval  finished. 

754...Bkan(  n  (i.M.i.i  i;n:>  a  i. a  I  loi.i  wpaisk.  These  galleries 
are  of  tin-  same  dimensions  as  small  branches;  the  frames  are 
made  of  plank;  they  arc  placed  touching  each  other,  arid 
serve  at  the  same  time  both  as  frames  and  sheeting. 

Each  frame  consists  of  four  pieces;  the  stanchions  have  a 
tenon  at  each  end,  Fig.  18,  fitting  into  notches  cut  in  the  cap 
sill  and  ground  sill  to  receive  them. 

When  the  gallery  is  an  ascending  or  descending  one,  the 
ends  of  the  staiichions  arc  cut  obliquely,  in  order  that  their 
sides  may  always  be  vertical. 

Fig.  1!'  is  a  plan  and  section  of  this  description  of  gallery. 

755. ..For  the  purpose  of  limiting  the  effect  of  explosion  of 
mines  upon  the  branches  leading  to  them,  and.  at  the  same 
time,  to  enable  the  miner,  acting  on  the  defence,  to  push  for- 
ward and  open  a  new  branch  toward  the  crater,  a  portion  of  & 
branch  leading  toward  the  mine  is  math'  of  heavy  frames  of 
the  foregoing  construction.  The  timber  recommended  for  the 
purpose  is  oak.  and  the  pieces  of  each  frame  are  \"2"  wide  and 
I"  thick.  The  portion  of  this  strong  framework,  at  the  ex- 
tremity, is  solidly  filled  in  with  pieces  of  4"  scantling,  from  G 
to  LO  feet  iii  length.  For  a  branch  28"  high  and  24" wide, 
m'ycii  horizontal  layers  will  be  required,  each  layer  consisting 
of  5  pieces.  The  centre  piece  of  each  layer  may  have  a  rope 
handle  at  its  end  to  allow  of  its  being  drawn  out  readily. 
Filled  in  this  way,  and  having  earth  well  packed  between  the 


mini-.  269 

pieces,  branches  of  this  description  will  not  be  damaged  by 
the  explosion  of  mines  of  from  6  to  10  feel  line  of  leasl   r< 
ance,    even    when    the   mines  are  within  41   to  6  feet  of  the 
branch.     From  their  cHief  object,  these  branches  arc  termed 
by  the  French  rameaux  de  combat. 

756.. .Shafts  a  i.\  Boule.  These  shafts  arc  lined  with  fram 
made  of  plank,  connected  togethei  as  shown  in  Fig.  20. 

In  Fig.  21,  a  section  of  a  shaft  a  la  Boule  is  shown,  which 
is  sufficiently  explanatory  to  render  any  other  description 
unnecessary. 

This  kind  of  shaft  can  only  be  used  with  advantage  in  favor- 
able >"il.  <>n  account  of  the  difficulty  of  introducing  the  frames 
sufficiently  near  each  other;  they  are  commonly  placed  one 
foot  apart,  as  shown  in  the  figure.  Large  gabions,  6  feet  long, 
and  from  .'!  feel  <i  inches  to  4  tcct  in  diameter,  arc  sometimes 
used  tor  Lining  shafts  near  the  surface,  smaller  gabions  being 
introduced  as  the  work  is  proceeded  with. 

757.. .For  the  purposes  of  quickly  establishing  small  camott- 
flete  and  fougasses,  a  boring  apparatus  has  been  resorted  t.-, 
the  diameter  of  the  boring  tool  being  4".     This  machine 
worked  like  ordinary  tools  of  litis  kind.     It  i.-  charged  for 

ion  by  inserting  powder  in  cylindrical  cartridges  of  some- 
what less  diameter  than  the  shaft,  which  are  well  rammed  for- 
ward; or,  if  a  large  charge  i-  requisite,  the  end  of  the  shaft 
can    he  enlarged   by  a  tool  with  a  joint,  which  will  admit  the 

gradually  to 
at  tin- end.  made  in  this  way  are  tern 

shafts  or  branch* 

758.   I         i  i.i  (  i  io\ 
floor  of  the  gall<  ry  i.~  not  more  than  10  or  12  feet  below 
surface,  it  will  b<  c-h  for  ti 

The  width  of  the  I  at  the  I  fl  he  the 

the  gallery  from  out  to  out     If  tic  soil  is  ven  H 

i  !y    ]..  r; 

above  tin  »uld 

be  left,  and  .  and   r><»  • 


270  mini.-. 

additional  depth  of  6  feet.    These  berms  serve  the  place  of 
scaffoldings,  to  pitch  tlie  earth  out. 

If  the  soil  is  very  loose,  the  slopes  will  require  to  be  bus* 
tained  by  a  sheeting  to  prevent  the  earth  from  caving  in. 
After  the  masonry  is  completed,  the  excavated  earth  is  care- 
fully replaced. 

V.V.i... When  the  construction  is  made  entirely  under  ground, 
a  wooden  gallery  is  first  formed,  the  width  of  which,  between 
the  frames,  in  the  clear.  Fig.  22,  is  equal  to  the  width  between 
the  piers  of  the  permanent  gallery  from  out  to  out;  its  height 
being  such  that  there  will  he  (!  inches  between  the  crown  of 
the  arch  on  the  exterior  and  the  cap  sills.  The  top  and  side 
sheeting  should  lap  about  8  inches. 

When  the  gallery  is  completed,  a  new  set  of  ground  sills  are 
laid  alongside  of  those  of  the  gallery,  their  length  being  equal 
to  the  width  of  the  permanent  gallery  in  the  clear,  Fig.  23. 
A  new  set  of  stanchions,  o,  o,  are  set  up  on  these  sills,  to  sup- 
port a  new  set  of  cap  sills  of  the  same  length  as  those  of  the 
gallery.  Vertical  hoards,  a,  are  placed  alongside  of  stanchions 
of  tin-  wooden  gallery,  and  are  buttressed  against  the  sheeting 
by  two  horizontal  pieces  of  scantling,  c,  <?,  one  near  the  top, 
the  other  near  the  bottom  of  the  gallery.  "When  this  new 
arrangement  is  completed,  the  frames  of  the  gallery  first  set 
up  can  be  taken  down,  and  the  masonry  commenced. 

The  foundations  of  the  piers,  Fig.  24,  are  laid  with  an  interior 
l  of  (i  inches.  The  piers  are  then  carried  up,  the  lower 
horizontal  buttress  being  gradually  shifted  up  so  as  not  to 
interfere  with  the  work,  and  the  lower  courses  of  the  side 
sheeting,  which  have  now  become  unnecessary,  being  removed. 
AVhen  the  piers  are  completed,  the  stanchions  are  taken  down 
and  replaced  by  pfops,  j>,  _£>,  resting  on  the  outside  of  the  tops 
of  the  piers. 

When  this  change  has  been  made,  the  way  is  clear  for  turn- 
ing the  arch.  For  this,  four  common  centres,  A,  A,  Figs.  25) 
26,  made  of  boards,  will  be  requisite.  Each  of  these  centres 
is  18  inches  broad,  and  is  secured  to  a  rectangular  frame,  o,  of 


MINKS.  271 

small  scantling  of  the  Bame  breadth,  and  as  long  as  the  span 
of  the  arcli.  Each  centre  thus  prepared  rests  upon  a  trestle, 
q,  y,  of  sufficient  height  to  bring  the  centre  in  its  trne  position 
to  receive  the  masonry. 

The  masons,  to  expedite  the  work,  commence  at  the  middle 
point  of  the  gallery,  where  two  of  these  centres  are  placed  to- 
gether, and  close  the  arch  over  them;  the  other  two  centres 
are  then  placed  alongside  of  these,  and  the  arch  in  like  man- 
ner is  elosed  over  them;  the  two  first  are  then  taken  down, 
and  removed  to  the  outside  of  the  two  last  Bet  up,  and  the 
arch  is  thus  carried  on  toward  the  two  ends.  The  wood 
work  of  the  gallery  is  taken  down  as  fast  as  the  masonry  sup- 
plies its  place. 

7»'»"...In  the  main  galleries  of  communication,  arched  rec 
are  formed  to  servo  as  depdts,  etc.,  for  the  implements  of  the 
miners.  These  recesses  are  from  6  to  1-  feet  in  depth  and 
usually  of  the  same  width,  and  may  be  placed  at  interval-  of 
15  or  l'1*  feet  from  each  other.  Similar  dispositions  are  made 
in  the  listening  galleries  for  the  magazines  of  earth  required 
for  tamping  the  mines ;  small  portions  of  galleries,  from  6  to 
12  feet  in  length,  are  run  out  at  right  angles  to  the  listening 
gallery  for  this  purpose.  A  sufficient  number  of  openii 
mn>t  al.~o  be  left  in  the  piers  of  the  listening  galleries,  for  the 
construction  o!  the  branches  leading  to  the  mine  chambers. 

761. ..In  I-  .  and  to  give  greater  r  irv 

galleries  to  glob< 

them  a  cross  section,  of  an  oval  form,  instead  of  th 
given.     Galleries  of  this  form  would  be  of  more  difficult  i 
strnetion  and  cost  more  than  those  of  the  usual  form. 

T62...When  Bevera]  galleries  branch  off  from  t1  point, 

a  large  arched  chambi  r  oi  a  sqn;  >nal  fori 

tructed,   which    s  ind    is   also  arrai 

with  a  crenated   wall   within  it  to  defend   the  rm 
galleries.     In  PI.  A.  cample,  if  tl 

//,  </,  meet  at  a  p  irched  cham 

to  com;-  i,   and    within  t: 


272  mines. 

thin  wall,  constructed  with  loop-holes  to  fire  in  the  direction 
of  tin-  most  advanced  galleries,  <',a,a. 

763...The  piers  of  the  galleries  are  also  arranged  either  with 
grooves  or  offsets,  so  that  harrier-  may  be  mad.'  within  them 
for  defence  against  the  enemy's  miner  when  he  penetrates 
into  tlic  gallery.  In  some  cases  a  simple  pit  is  dug  across  the 
gallery  and  covered  by  boards,  which  are  taken  up  when  the 
communication  is  required  to  be  cut  off. 

764.. .Mini:  Chambers.  The  chamber  of  a  mine  is  a  cavity, 
A,  formed  to  receive  the  charge  of  powder.  Fig.  L'T. 

When  the  chamber  is  made  at  the  end  of  a  gallery,  the  cen- 
tre of  the  chamher  is  placed  on  a  level  with  the  floor  of  the 
gallery.  It  is  usually  better  to  place  the  chamber  at  the  end 
of  a  small  branch  return  on  one  side.  When  the  charge  is 
not  to  be  exploded  immediately,  or  the  ground  is  much  satu- 
rated with  moisture,  it  should  be  placed  in  a  well  pitched 
wooden  case,  or  a  good  cask,  or  in  a  wooden  case  covered  with 
tarpaulin,  or  any  like  expedient  adopted  that  may  he  at  hand — 
the  best  receptacle  is  a  water-tight  tin  case. 

In  dry  ground,  and  when  the  charge  is  to  be  soon  exploded, 
canvass  hags  will  answer. 

If  the  case  to  contain  the  powder  is  not  more  than  2  feet 
square,  it  may  he  introduced  into  the  chamher  ready  made  ; 
if  of  a  greater  dimension,  it  must  he  put  together  in  the  cham- 
her, the  pieces  to  form  the  sides  being  arranged  like  the  frames 
ot  branches  a  la  ]I.<>Ihin<I<t.ix<\ 

An  ppening  is  left  at  the  edge  of  the  cover,  about  4  inches 
square,  for  the  introduction  of  the  charge,  and  a  similar  one 
in  the  side  to  receive  the  hose-trough. 

The  edge  of  a  cubical  case  to  contain  a  given  charge  is  cal- 
culated on  the  supposition  that  58.5626  pounds  of  powder  are 
equal  in  hulk  to  a  cubic  foot;  and  l,(»oo  cubic  inches  will, 
therefore,  contain  33.89  pounds.  From  this,  if  J'  represent! 
the  given  number  of  pounds  of  powder,  and  X  the  side  of  the 
cubic  sought  in  inches,  then 


mini  b.    -  273 

33.80 :  (io)8::P:  .r3, 

X=3.W{-  /'. 
That  is,  to  obtain  the  edge  of  the  cubical  case  in  inches,  ex- 
tract the  cube  root  of  the  given  number  of  pounds  of  powder 
and  multiply  it  by  8.09,  or  3  L-10,  nearly; 

From  the  bursting  of  guns,  where  the  wad  has  not  been 
pressed  down  on  the  powder,  it  has  been  thought  that  in 
charging  mines  a  like  increase  of  effect  would  be  produced, 
by  leaving  a  certain  free  spacearound  the  case.  Experiments 
on  this  point  have  not  been  sufficiently  decisive  to  lead  to  the 
adoption  of  this  in  practice. 

765... Hose  TrouoHs.  The  hose  trough  is  a  small  wooden 
channel,  in  which  is  placed  a  linen  bag  tilled  with  powder, 
and  termed  the  powder-hoee,  to  tire  the  charge. 

The  bag  should  be  of  close  texture  and  well  sewed. 

These  troughs  are  made  L£  inch  square  in  the  clear.  Tlic 
four  pieces  of  which  they  are  composed;  the  sill,  sides  and 
top.  or  cover,  are  from  J  to  h  inch  each  in  thickn* 

A  trough  should  penetrate  the  powder  case  about  1  incl 
and  should  exactly  tit  the  opening  left  for  it. 

It    i.-  fasti  rti  d   to  the  floor  of  the   branch    by  nails,  through 
the  -ill,  which  enter  small   pickets  driven  to  receive  them. 
Sora<  times  the  eidi  -  of  the  trough  arc  confined  by  picket 
prevent  its  being  disturbed. 

The  different  lengths  of  the  trough  should  be  cut  to  tit  ex- 
actly.    Each  portion  of  the  trough  should  have  its  cover  well 
fitted    and    secured  with   one   peg  only,  in    order    that    it    may 
moved  to  introduce  the  powder-hi 

The  trough  i-   said   to  make  an    elbow  when    it 
direction.     The  pi<  c<  e  forming  an  elbow  should  be  firmlj 
simply  connected;   I  "•',  show  the  mo  I 

of    cIIm.v 

766. ..Proportioning  Trains.  When  several  mines  are  to 
be  tired  at  i •  moment,  it  rtion 

r  trains  that,  starting  from  tl 


274  min 

time  from  that  point  to  the  charges  may  be  all  equal.  The 
following  cases  Bhow  the  manner  of  obtaining  this  result: 

For  two  charges,  Fig  30,  place  a  trough  on  the  shortest  line 
from  the  one  to  the  other,  mark  the  centre  of  it,  and  lei  the 
principal  trough  join  it  in  that  point* 

For  three  charges,  Fig.  31,  connect,  as  above,  the  two  which 
are  nearest.  Let  a  trough  from  the  middle  point  of  this  to  the 
third  ehargej  biseel  tin-  whole  length  of  trough  between  this 
third  charge  and  either  of  the  others;  then  let  the  principal 
trough  be  joined  to  this  last  point. 

For  four  charges,  Fig.  32,  first  connect  them  two  and  two, 
then  join  the  central  point.-  and  proceed  as  above. 

The  elbows  of  a  trough  impede  the  communication  of  the 
fire,  for  which  an  allowance  must  1k>  made  when  proportioning 
the  trains,  each  elbow  being  valued  at  3  inches;  thus,  it'  on 
one  side  of  the  point  where  the  principal  trough  connects  is 
one  elhow  more  than  on  the  other, the  principal  trough  should 
he  placed  :;  inches  nearer  to  the  charge  on  that  side,  which  is 
done  by  placing  it  14-  inches  from  the  central  point  toward 
that  side.  Square  elbows  impede  somewhat  more  than  oblique 
ones. 

Experience  has  Bhown  that  two  powder-hoses  may  be  placed 

within  is  inches  of  one  another  if  covered  with  earth,  and  ex- 
ploded separately  without  interference. 

707... Tamping.  Mines  are  tamped  either  with  earth  and 
sods,  with  earth  and  wood,  or  with  sand-bags. 

To  tain])  a  branch  with  sods  and  earth,  the  miner  first  tills 
the  branch  with  sods  lor  a  length  of  3  feet,  commencing  at  the 
ehamber.  The  sods  are  piled  in  regular  layers,  the  precau- 
tion being  taken  to  throw  loose  earth  over  each  layer,  to  fill 
the  voids  between  the  sods.  When  this  length  is  finished,  the 
miner  lills  in  for  an  additional  '■'>  feet  with  earth,  which  should 
he  well  packed.  Another  Ipngth  of  sods  is  laid  of  3  feet,  and 
so  alternately  through  the  entire  branch. 

To  tamp  with  wood  and  earth,  a  stout  shield  of  thick  hoards 
is  first  placed  across  the  branch  and  firmly  buttressed  against 


M!\  275 

the  chamber,  the  branch  is  then  filled  with  well  packed  earth, 
resting  against  the  shield  for  a  length  of  •">  feet;  billets  of 
round  <u-  square  timber  are  then  packed  across  the  branch  for 
a  Ldngth,  likewise,  of  8  feet ;  another  length  of  earth  of  the 
same  thickness  is  packed  in  against  the  Wood,  and  bo  oil  for 
the  entire  length  to  be  tamped;  finally,  at  the  end  of  the 
tamping  another  shield  is  set  up  and  firmly  buttressed. 

Sand-bags,  for  tamping,  are  of  the  ordinary  dimensions.  To 
tamp  with  them,  a  shield  is  first  placed  against  the  chamber 
and  well  buttressed.  The  branch  is  then  filled  up  with  sand- 
bags laid  in  regular  Layers,  loose  earth  being  thrown  over  each 
layer  to  close  the  joints.  This  U  the  best  kind  of  tamping, 
it  can  be  removed  most  s] lily  after  the  explosion. 

The  length  of  tamping  is  regulated  by  the  line  of  least  re- 
nee  of  the  mine;  the  part  <>f  the  branch  tamped  equal  to 
twice  this  line.  This  length  must  he  measured  in  a  right  line 
from  the  chainher  to  the  point  of  the  branch  where  the  tanip- 
ing  terminates,  and  not  along  the  windings  or  elbows  of  the 
branch. 

768. ..As  tamping  is  a  laborious  operation,  and  requires  con- 
rable  time  to  do  it  thoroughly,  it  has  been  proposed  to 
insert  a  trough  of  4"  or  5"  section,  in  tin-  branch  or  -haft  lead- 
ing from  the  mine  chamber  to  the  main  gallery,  or  branch, 
and  then  to  tamp  in  the  usual  manner  around  the  trough. 
Prepared  in  this  way,  the  charge  made  into  cylindrical  car- 
ta powd<  \  >■  portions  in  a 
cylindrical  vessel,  attached  by  a  joint  at  it.-  bottom  to  tin 
of  a  rod,  can  bi  I  through  the  trough  and  be 
thrown  into  the  chamber  in  a  very  short  time,  and  I 
he  immediately  afterward  explo  I 

769.. .Id  ethoi  common  methods 

firing  mil  by  tin  \k  and  the    ; 

i  two  method 

The  monk  i>  a  bit 
to  he  tired  by  it 


276  mines. 

* 

sprinkle  some  dry,  fine  powder  on  it:  cover  this  powder  < 
with  another  sheet  of  paper,  secured  at  its  four  corners  with 
»lrv  earth  or  stones;  pass  the  monk  through  a  hole  in  the 
apper  sheet,  and  Let  it  project  half  its  length  above  it,  its  : 
being  plunged  in  tire  powder  on  the  bottom  sheel  ;  set  fire  to 
the  monk  at  top  with  another  piece  of  agaric,  termed  an  in- 
fm  m<  r,  of  the  same  dimensions  and  form  as  the  first,  and  retire 
quickly. 

The  bOXrfcrap,  Fig.  33,  is  a  box  18  inches  high  and  n'  inches 
wide  in  the  clear.  The  bottom  consists  o\'  a  piece  of  plank 
18  by  Id  inches,  and  its  cover  is  fixed  at  one  side  only  with  a 
wooden  pin,  about  which  it  can  be  turned. 

At  6  inches  from  the  top  of  the  box  a  horizontal  slit  is  made 
in  one  of  its  sides,  and  grooves  in  the  two  adjacent  to  it.  t<> 
receive  a  piece  of  hoard,  which  ought  to  slide  freely  in  this 
arrangements.  In  the  lower  part  of  the  box  an  opening  is  left 
on  the  side  opposite  the  one  cut  for  the  slide,  to  admit  the 
powder-hose. 

To  fire  the  train,  place  the  box  against  the  extremity  of  the 
tamping  and  secure  it  well ;  tie  a  string  to  the  slide,  and  lead 
it  along  the  stanchions  of  the  gallery  on  pegs  driven  for  that 
purpose  ;  put  the  end  of  the  hose  into  the  hex  through  the 
hole  left  for  it,  and  spread  on  the  top  of  it  some  dry,  tine  pow- 
der; then  put  in  the  slide  and  close  with  earth,  or  rags  of  sand- 
hags,  all  communication  between  the  lower  part  of  the  box 
and   the   branch  ;  place  a  star-match  of  six  or  eight   points, 

Well  lighted,  on  the  Blide  :  replace  the  cover,  then  pull  the 
string  and  the  star  will  fall  below  and  fire  the  mine. 

The  two  methods  above  described  have  the  inconvenience 
of  requiring  a  powder-hose,  which,  from  its  own  explosion, 
poisons  the  galleries.  They  have  also,  and  more  particularly 
the  monk,  the  defect  of  not  producing  the  explosion  always  at 
the  instant  desired. 

To  avoid  these  inconveniences  a  galvanic  current  has  of  late 
been  applied   to  lire   mines,  and  with  complete  success.     This 


MP-  L'77 

method    has   been   found    particularly   serviceable   in   firing 
charges  under  water. 

A  small  rocket,  Fig.  34,  with  a  hemispherical  head  of  wood, 
lias,  also,  been  tried  successfully.  To  use  it.  a  wooden  trough 
with  a  smooth  interior  must  be  placed  from  the  charge  to  the 
point  where  the  rocket  is  to  start :  tin  tul>es  have  been  recom- 
mended, but  are  found  not  to  answer.  The  rocket  i-  then 
placed  in  the  end  of  tin-  trough,  the  quick-match  with  which 
it  i>  provided  is  lighted,  ami  the  rocket  start.-  with  very  Lrre:it 
velocity,  penetrates  the  charge  and  fires  it. 

When  the  rocket  lias  to  pass  elbows,  or  when  it  is  desired  to 
fire  several  mines  at   tlie   same    moment,  q  rocket  is  placed    at 
each  turn  of  the  trough,  with  it.-  quick-match  secured  round  a 
nail  ;  the  first  rocket  arriving  at  the  point  where  the  oth<  i 
placed  fires  it.      In  order  the  Letter  to   insure    the    first    rocket 

firing  tl  d.  a  quantity  of  powder  (^  ounce)  should  lie 

BtroWU  about   the    match   of  the    latter,  protected  by  a  wed 
lhaped    slip    of  deal,    nailed    to  the  bottom  of  the  trough  ;    the 

rocket  meeting  this  |  »ver  the  powder,  which  its  rapid 

motion  would  otherwise  disperse. 

A   rocket  may  be  made  to  turn  in  a  circular  trough,  when 

■ 

the  radius  of  that  part  is  not  Less  than  twice  the  h  ngth  of  the 
rocket. 

In  order  to  prevent  the  Bmoke  of  the  charge  pcn<  trating  the 
gallery  through  the  trough,  one  (,r  two  small   iron   traps   i 
lie  j. laced  in  the  trough,  which.  .    by  the   ro< 

fall  again  by  their  own  weight,  and  cut  off  all  commui 
between  the  gallery  and  the  charg 

A  rocket  6  inches  long  will  travel   100  yards, 
it.-  velocity  :  si  that  ts  .  ed  at  t1 

Brent,  to  run    very    different 
interval  in  the  times  of  their  arrival.     Th 

proportion  I 
simultaneously,  which  with  powd< 

The  ordinary  rocket  I 

in  d  2-5  of  fit 


278  MI.N 

and  l-.r»  of  charcoal  dust.  These  ingredients  should  be  very 
carefully  mixed,  to  make  the  rocket  burn  uniformly.  Its 
Usual  diameter  is  nearly  f  of  an  inch,  and  its  entire  weight 
about  H  ounce.  Rockets  may  be  made  much  smaller  when 
required. 

7T.0...The  great  advantages  offered  by  galvanic  batteries  for 
exploding  mines  at  considerable  distances  from  the  battery, 
either  when  isolated  or  combined  in  groups  for  simultaneous 
effects,  have  led  to  experiments  which,  from  the  uniform  cer- 
tainty of  the  results,  besides  other  obvious  advantages  over 
any  of  the  other  methods  above  given,  will,  probably,  cause 
the  genera]  adoption  of  this  apparatus  for  military  min 

The  method  mostly  adopted  by  the  Continental  engineers  is 
tlu'  combination  of  Bunsen's  battery  with  Ruhmkorf's  appa- 
ratus for  intensifying  the  current  of  induction.  A  copper 
conducting  wire,  which  is  insulated  by  one  or  two  coats  of 
gutta-percha,  connects  the  charges  with  the  galvanic  appara- 
tus, The  charge  is  exploded  by  passing  a  .-park  through  a 
very  small  portion  of  fulminate  of  mercury  inserted  between 
the  ends  of  two  popper  wires,  which  are  enclosed  within  a 
short  tuhe  of  gutta-percha,  coated  within  with  sulphuret  of 
copper.  The  wires  are  bent  near  the  end  of  the  tube,  ami 
twisted  around  each  other.  A  little  meal  powder  is  thrown 
around  the  fulminate  and  the  tuhe,  which,  with  the  tube  and 
the  bent  part  of  the  wire,  is  tightly  closed  in  a  small  gutta- 
percha bag,  t«>  keep  out  moisture.  To  fire  a  single  mine,  one 
end  of  the  twist  is  soldered  to  the  conducting  wire  and  the 
other  inserted  into  the  earth  to  complete  the  circle,  for  sev- 
eral mines,  to  he  exploded  at   the  same  time,  Conducting   wires 

conned  the  mines,  and  tlu-  ends  of  the  twist  are  soldered  one 
to  each  conductor,  except  the  end  one,  which  has  one  of  its 
ends  inserted  into  the  earth.  By  this  combination,  the  series 
will  be  exploded  without  any  sensible- ^difference  of  time  be- 
tween the  nearest  ami  furthest  mine. 

771... Blasts.  Blasts  are  small  chambers,  or  holes  made  in 
rock,    or    masonry,    charged    with  powder.     The  forming   of 


mi\  279 

blast-holes  requires  the  uso  of  particular  toots,  called  borers, 
jumpers,  scrapers,  needles,  and  tarrvpirig-bwrs. 

To  form  the  blast-hole,  two  or  three  men  arc  required  ;  one 
holds  the  borer  with  both  hands,  while  the  head  of  it  is  struck 
with  sledge-ham  mere  by  one  or  two  others.  The  first  turns 
the  borer  at  each  stroke  so  thai  the  hole  may  be  circular,  and 
from  time  to  time  clears  it  out  with  the  scraper. 

When  the  hole  required  does  not  exceed  [5  inches  in  depth, 
it  may  be  excavated  in  the  above  manner;  but  if  20  inch<  -  o# 
more  deej.,  the  jumper  is  generally  made  use  of.  The  miner 
holds  the  jumper  in  both  hands,  raises  it.  and  lets  it  fall  in  the 
hole,  turning  it  continually;  he  also  clears  the  hole  with  the 
scraper.  When  the  Btone  is  of  a  very  hard  description,  it  is 
usual  to  pour  wat  rionally  into  the  jumper  hole. 

To  load  the  hole,  fill  about  one-fourth  or  one-third  of  it  with 
powder,  according  to  the  nature  of  the  stone.  The  charge  fof 
a  depth  ol   Is  in  ft  "in  8  to  1 2  oun< 

T<»  tamp  and  prime  the  blast  hole,  the  needle  is  first  intro- 
duced, plunging  it  well  into  the  powder  and  placing  it  on  the 
smoothest  side  of  the  hole;  then  a  layer  of  clay  is  laid  on  the 
powder,  and  is  closely  pressed  down  with  the  tamping-bar. 

(  Mher  similar  layers  are  then  hod.  or  layers  of  brick  redu< 
to  .-mall  bits,  the  needle  being  turned  repeatedly.     It  is  at 
to  press  down  the  first  layers  with  a  bar  of  wood— the  b< 
of  a  tool  lor  instance — and  the  latter  ones  with  the  iron  tamp- 
ing har.     When  the  hole  i.~  thus  filled  up,  a  small  shell  of  - 
is  formed  round  the  needle,  which  i>  then  withdrawn,  the  hole 
left  by  it  i.~  filled  with  fine  powder,  and  it  i>  tired  with  a  monk 
or  a  1  port-fire. 

The  use  of  the  n<  1  die  ;-  often  dispensed  with,  in  which  c 
the  priming  i>  rolled  up  in  a  brown  paper,  or   ■ 

traduced  in  straw  thrust  into  one  another.     I       prii 

aced  in  the  hole  at  th 
may  pent  tratc  wed  into  the  !.,••.  1 .     p.,    tan  , 
cuted  a-  before. 

Tl; 


280  MINES. 

also  be  dispensed  with,  the  hole  being  filled  over  the  charge 
with  wry  fine  dry  sand,  poured  in  witboul  any  pressure. 

The  many  accidents  that  have  happened  in  priming  Masts 
have  led  to  the  invention  of  priming-fuses,  wh'.^h  are  mad 
burn  somewhat  in  the  same  way  as  the  fuse  in  the  small  Chii 
fire-cracker.    Their  use    is  far  safer  than  any  of  the  former 
metli< 

Fur  blasts  under  water,  the  charge  is  inserted  in  a  water- 
tight tin  ease,  and  fired  either  by  a  galvanic  current  or  a  prim- 
ing-fuse, which  is  protected  from  the  water  by  a  small  tube 
connected  with  the  charge,  and  leading  to  the  surface  of  the 
water. 

The  result  of  many  experiments  has  shown  that  in  blasting 
rock  a  large  portion  of  the  powder — nearly  halt — may  he 
saved,  by  mixing  with  the  remaining  part  tine  dry  sawdusl  <>f 
elm  or  beech.  In  blasts  exploded  in  this  way,  the  effect  is  not 
the  same  as  when  the  full  charge  of  powder  is  used  ;  the  rock 
splits  into  fewer  and  larger  pieces,  and,  to  finish  dividing 
them,  a  more  frequent  use  of  the  sledge-hammer  is  required. 

772...1  >i.moi.itions.  Xhe  charges  of  mines  intended  to  over- 
throw masonry,  are  calculated  as  in  a  common  soil,  by  using 
the  proper  quantities  given  in  the  preceding  table  for  the  dif- 
ferent kinds  of  masonry  to  be  destroyed. 

773...To  r.Ki.M  11  a  Wall.  First  ascertain,  if  practicable^ 
the  thickness  of  the  wall,  and  then  proceed  thus : 

JFirfit  case.  When  the  wall  is  from  2  to  3  feet  thick,  place 
one  or  two  barrels  of  powder  against  the  lower  part  of  it,  and 
fire  them. 

Second  case.  When  the  wall  is  from  5  to  G£  feet  thick,  place 
One  or  two  charges  under  its  foundations,  plumb  with  the 
centre  of  the  wall. 

Third  case.  When  the  wall  is  from  9  to  L2  feet  thick,  open 
at  the  foot  of  it,  or  about  L2"  above  the  water  level,  a  branch 

gallery,  which  must  be  driven  to  the  centre  of  the  wall  ;  then 
make  two  perpendicular  returns  to  this  branch,  and  place  the 
powder  at  their  extremities]  Fii^.  35. 


MINI  ■>.  281 

774. ..To  Bbeagh  a  Wall  with  a  Tikkaoe.  Open  at  the 
foot  of  the  wall,  or  1*2"  above  the  level  of  the  water,  a  branch 
perpendicular  to  the  direction  of  the  revetement;  drive  it 
through  (lie  wall  to  the  earth,  then  make,  to  the  righl  aftd  left, 
two  other  branches,  following  the  hack  of  the  wall,  and  each 
in  length  equal  to  its  thickness;  place  the  charges  at  the  end 
of  these  branches,  so  that  the  centre  of  each  charge  may  be 
flush  with  the  hack  of  the  wall. 

?76...Demolttion  of  Revetements.  When  the  revetement 
is  withont  counterforts,  or  the  counterforts  are  not  more  than 
3  feet  thick,  several  branches  are  driven  perpendicular  to  the 
direction  of  the  revetement,  at  equal  distances  apart.  The 
charges  used  should  produce  craters  that  will  cross  each  other 
a  little. 

When  the  wall  baa  counterforts  of  the  usual  dimensions,  the 
charges  are  placed,  as  far  as  practicable,  in  the  lines  of  their 
axes  and  their  junction  with  the  revetement,  Fig.  36. 

When  time  presses,  instead  of  making  one  branch  for  each 
pair  of  charges,  one  is  made  for  each  charge;  and  the  whole  of 
the  charges  are  placed  at  three-fourths  of  the  thickness  of  the 
wall,  and  so  regulated  that  their  craters  may  slightly  run  into 
each  other.  Fig.  87. 

When  galleries  cannot  be  driven  at  the  proper  level  for  the 
charge,  a-  in  the  demolition  of  wharves,  etc.  shafts  are  sunk 
behind  the  revetement,  or  at  a  Bhoii  distance  in  the  Pear  of  it, 
big.  :;**.  and  branch''-  are  then  driven  to  the  positions  tor  the 
charges;  or.  which  is  still  better,  becanse  it  is  a  more  sp< 
operation,  a  shaft  may  be  sunk  for  each  cha 

The  depth  of  the  shaft  mntl  be  sufficient  to  admit  ^ 
proper  length  of  tamping. 

If.  at  the  same  time  with  the  wall,  a  n  arth  in  I 

rear  of  it  is  to  be  destroyed,; prolong  the  branches  in  the  in- 
terior of  the  earth  sufficiently  t<>  allow  of  the  □ 
back  of  the  wall  exploding  before  those  placed  in   the  earth 

W     •    .  '    •        ;-  a  eralh  of  the  r< 

36 


282  mini-. 

ment,  the  charges  should  be  placed  along  this  gallery,  exca- 
vating chambers  fotf  them  in  the  revetement  at  distances  apart 

equal  to  twice  their  line  of  leas:  resistance,  viz.;  at  two  lined 
intervals. 

The  portions  of  the  gallery  in  the  rear  of  the  charg* 
then  tamped;  at  each  end,  the  length  of  the  tamping  should 
be  equal  to  twice  the  line  of  least  resistance  of  the  extreme 
charges. 

The  following  method  has  been  employed  with  success. 
Regarding  as  the  tine  of  least  resistance  the  distance  from  the 
gallery  to  the  surface  of  the  wall,  imagine  a  r«>w  of  common 
mines  placed  at  two  lined  intervals  throughout  the  length  and 
calculate  the  sum  of  their  charges,  to  which  add  one-half  for  a 
great  gallery ;  place  the  whole  charge  in  several  heaps,  with 
strong  trains  leading  from  one  to  another.  Then,  tamp 
strongly  and  carefully  the  ends  ot  the  gallery,  leaving  the 
space  intended  to  be  demolished  void.  When  the  galler 
more  than  2  yards  wide  and  high,  or  if  it  have  many  ieSUea 
difficult  to  tamp,  the  charge  of  powder  must  be  farther  aug- 
mented to  produce  the  desired  effect. 

TY6...Dbmouttob  ok  Towebs.  If  the  interior  diameter  of 
the  tower  be  6  yards  or  more  Fig.  41,  drive  branches  into  a 
wall  from  the  interior  of  the  tower,  and  place  charges  80  as  to 
be  a  little  nearer  to  the  interior  than  to  the  exterior  of  the 
wall.  When  the  tower  is  connected  with  walls,  charges  must 
Ik-  placed  at  their  points  of  junction. 

When  the  tower  is  but  4  or  5  yards  in  diameter,  Fig.  Il\ 
sink  a  shaft  to  about  the  level  of  the  bottom  of  the  foundations, 
and  place  a  charge  there  corresponding  to  the  line  of  least 
resistance,  measured  from  the  centre  of  the  charge  to  the 
foot  of  the  wall  outside. 

Cover  the  floor  of  the  tower  with  two  rows  of  small  beams, 
then  lay  upon  them  two  beams  crossing  and  halved  into  one 
another;  and  place  upon  these  uprights  abutting  firmly  against 
the  masonry  of  the  arch. 

When  a  shaft  cannot  be  sunk  on  account  of  water,  and  when 


MINES.  283 

the  tower  has  loop-holes  which  prevent  charges  being  plated 
in  the  walls,  lay  the  charge  on  the  floor  of  the  tower,  enclosed 
in  a  strongly  constructed  case,  propped  on  all  side*  against 
the  masonry. 

When  the  tower  is  square,  and  has  several  floor!  or  Btagee, 
the  charges  may  lie  placed  at  the  four  corners  of  the  ground 
story,  tamping  the  tir^t  lloor. 

777...I>KM<u.rnox  OF  PoWDEB  Maoaxjxks.      Place    chars 
the   piers   and    ^able   ends,    so   that  their  craters  may  slightly 
cross  each  other. 

When  time  presses,  a  charge  is  laid  on  the  floor  of  the  mag- 
azine, the  doors  are  barricaded,  and  it  is  tired  with  a  hose  led 
outsiile. 

To  determine  the  quantity  of  powder  required  for  the  heap, 
calculate  the  number  of  common  mine.-  required  to  overturn 
a  revetement  of  tin1  same  length  and  thiclcness  as  the  walls 
a  magazine,  including  the  piers;  add  pne-half  the  sum  of  the 
charges  tlm*  found,  and  place  the  whole  in  one  heap  in  the 
centre  of  the  magazine. 

The  above  method  is  only  applicable  to  magazines  of  not 
more  than  150  square  yards  surface.  If  of  greater  capacity, 
the  quantity  first  found  should  be  increased  1-1"  for  every  15 
Square  yards  of  additional  surface,  and  be  placed  in  tw 
more  heaps,  connected  with  powder-hose  to  tire  them  simul- 
taneously. 

77v..l  M  M"i  iiion  oj    |',i;;  _,.,  the  piers 

of  which  are   from   !  to  J         '  thick,  place  in  one  of  the  piers 
two  oharges  oJ   130  to  160  pounds  each,  1 
plana  to  the  bridge  op  which  to  place  the  powder-h 

I:  the  pii  r  be  from  6  to  L0  fo<  I  thick,  drive  in  the  middle  of 
it,  parallel  to  small:  ,  at  the  ends  of  wb 

place  charges  of  from  200  1  i. 

When  there  is  not  time  to  place  charges  in  the  interior  of 
the  j  the  arch   l  - 

ler. 


284 


MINES. 


This  quantity  of  powder  lias  broken  semicircular  arches  of 
eel  >]>an.  and  -1A  feel  thickness  al  the  crown. 

Another  good  method  is  t<»  cul  a  trench  in  the  form  of  a 
cross.  Fig.  1 1,  over  the  middle  ot'  the  arch,  each  branch  being 
about  LO  feet  long,  and  carried  down  t<>  the  extrados.  Place 
in  each  branch  200  pounds  of  powder  for  an  arch  3^  iect 
thick,  and  cover  the  charges  with  timber,  earth,  etc. 

An  arch  may  also  be  blown  up  by  suspending  an  open 
trough  nnder  it  with  cord.-,  and  placing  in  it  charges  of  pow- 
der similar  to  those  already  stated  fior  trendies  cut  on  the  .sur- 
face. 

When  tin'  savin--  of  powder  is  of  consequence,  sink  a  Bhaft 
down  to  one  of  the  haunches,  Fig.  45,  and  place  the  powder 
in- one  mass,  unless  the  bridge1  be  very  wide.  An  arch  of  18 
inches  or  2  feet  thickness,  of  a  bridge  20  feet  wide,  may  thus 
be  destroyed  with  45  pounds  of  powder,  if  a  loading  can  be 
applied  over  the  charge,  giving  an  equal  resistance  to  the  arch. 

If  the  bridge  is  more  than  20  feet  wide,  two  shafts  must  be 
sunk,  and  charged  as  before  described.  When  the  side  walls 
of  the  bridge  above  the  piers  are  slightly  built,  and  the  load- 
ing of  the  arch  is  of  loose  rubbish,  a  small  gallery  should  be 
driven  about  5  or  6  feet  from  the  arch  stones,  along  the  axis 
of  the  pier,  as  at  A\  Fig.  45;  a  return  is  then  made  toward 
the  arch,  and  the  charge  is  placed  in  contact  with  the  ex- 
trados. Bridges  of  timber  may  be  blown  up  by  suspending 
barrels  of  powder  under  one  or  several  bays. 

779... Demolition  of  Houses.  Begin  by  undermining  the 
windows  and  doors,  and  cutting  away  the  piers  between  them, 
so  as  to  leave  the  building  supported  by  a  *ew  piers  only, 
nearly  square.  Place  in  each  of  the  piers  a  charge  of  from 
13  to  16  pounds  of  powder,  tamping  well  with  wood.  Pro- 
portion the  trains  to  the  different  charges,  so  that  they  may 
be  simultaneously  exploded.  If  pressed  for  time,  resort  to 
the  same  methods  as  for  towers  and  galleries. 

To  destroy  palisades,  or  gates,  doors,  etc.,  the  best  method  is 
to  suspend  a  leathern  bag,  filled  with  powder,  either  with  a 


mini-.  285 

forked  stick,  a  strong  gimblet,  ot  a  stout  copper  nail,  against 
tlif  gate  or  palisade.  The  bag  should  have  about  an  inch  of 
port-fire  tirmly  secured  in  one  side  of  it,  to  communicate  the 
lire  to  the  charge.  To  throw  down  a  strong  palisade,  from  30 
to  50  pounds  of  powder  should  be  used.  To  burst  open  a 
town  irate,  60  or  7"  pounds  of  powder  will  be  required^ 

780..'.Fotf€U£SEB.  Mines  are  so  called  when  placed  at  the 
bottom  of  small  shafts,  from  9  to  12  feet  deep.  The  powder 
is  Lodged  in  one  of  the  sides  of  the  shaft,  and  it  is  fired  from  a 
secure  spot  by  means  of  a  powder  hose,  brought  up  one  side 
of  the  shaft,  and  carried  in  a  trough,  parallel  to  the  ground,  ■> 
or  6  feet  below  the  surface.  When  there  is  no  occasion  to  fear 
that  sheik  may  fall  on  the  part  where  the  trough  is  laid,  it 
will  be  sufficient  to  place  it  '2  or  2£  feet  under  the  ground. 
The  powder  case  and  trough  should  be  well  pitched,  the  shaft 
tamped  in  the  strongest  manner,  and  the  earth  round  about 
the  shaft  be  dug  over,  that  nothing  may  indicate  to  the  enemy 
the  position  of  the  fougasse, 

7^1. ..Sin  i.i    I"oi  •  Shells  may  be  huricd  singly,  Of  in 

Bmall  heaps,  and  be  made  to  burst  either  under  the  ground  or 
on  its  surface. 

If  they  are  to  burst  under  the  earth,  they  must  be  sufficiently 
charged  to  produce  a  crater,  through  which  the  pieces  are  pro- 
jected. 

Jt'  they  are  to  burst  on  the  surface,  the  requisite  quantity  of 

powder  to  produce  a  crater  and  throw  out    the  shells   must 

lodged  under  them,  while  these  latter  need  only  have  a  suffi- 
cient charge  to  burst  them. 

In  all  cases  a  box  is  at  livided  into  two  parts  by 

a  partition.  The  shells  are  placed  in  the  upper  part,  their 
fuses  project  through  the  partition,  and  extend  from  £  to  1  inch 
below  it. 

In  the  lower,  part,  the  hose  only  is  placed  when  the  shells 
are   intended  to  produce   their  own  crater;  but   |  auffi- 

I   to  produce   th< 
tended  to  burst  on  ti  md. 


286 


MINES. 


Tin'  effects  produced  by  common  and  shell  fougasses  are 
very  Limited,  and  only  destructive  near  their  craters:  con- 
sequenjkly,  they  should  not  be  exploded  until  the  enemy  is 
above  theui. 


Dks<  iui'tkin  ok  Shell. 

¥\  i.i.  I.'iiai;i;k   OF  thk 
Sn  k  i.i.. 

IlMllI      AT     WHICH     THK      KILL 

(  iiaki.k    rkoin  i'KS  A 
I'UATKK. 

Lbs. 

Oz. 

Calibre,    5  J 

1 

0 

2' 

0" 

8 

2 

9 

2 

10 

"       10 

5 

0 

3 

6 

"       13 

11 

0 

■ 

4 

7 

782.. .Conditions  to  bk  Satisfied  in  Aunam.im.  a  System  of 
"Minks. — As  the  galleries  of  a  system  of  mines  serve  the  pup* 
pose  of  underground  communications,  they  should  he  subjected 
to  the  same  conditions  as  other  Communications.  A  condition 
of  primary  importance  is.  that  no  combination  shall  be  made 
which  might  compromise  the  safety  of  the  enceinte.  To  this 
(iid,  no  gallery  under  the  glacis  should  lead  to  the  interior  of 
the  enceinte;  for,  should  the  enemy  get  possession  of  such  a 
gallery,  he  might  either  penetrate  into  the  work  or  else  barri- 
cade the  gallery  and  hold  possession  of  it  long  enough  to  blow 
up  the  works  under  which  it  leads. 

783. ..The  galleries  should  not  offer  any  facilities  to  the  be- 
siegers for  carrying  on  their  works.  Those  galleries,  therefore, 
which,  debouching  in  the  ditches,  might  serve  the  besiegers 
fortheir  descent  of  the  ditch;  also,  a  continued  counterscarp 
gallery,  which  may  not  only  facilitate  the  descent  of  the  ditch 
of  the  besiegers,  but,  also,  when  in  their  possessionj  give  them 
that  of  the  whole  sy.-tem,  and,  besides,' serve  to  protect  their 
passage  of  the  ditch,  and  to  prevent  sorties  in  it,  should  be 
rejected.     A  gallery  behind  a  portion  of  the  counterscarp  not 


MINT-.  287 

favorable  to  the  enemy's  works,  is  very  useful  as  a  depoi  for 
the  implements  of  the  miners,  and  also  as  a  communication. 

TW...A  permanent  system  ef  mines  should  not  be  osed, 
either  for  works  that  can  be  carried  by  storm  or  for  covered- 
Ways  in  a  similar  state:  for  the  reason  that  the  besiegers 
might  easily  get  possession  of  the  system  before  it  could  he 
brought  into  play. 

Z85.«.The  debouch^  of  a  system  in  the  ditches  nnist  he  re- 
vetted, to  offer  a  sufficient  obstacle  to  prevent  the  enemy  from 
getting  possession  Of  the  system  by  surprise;  hence,  a  revetted 
counterscarp  is  a  necessary  condition  in  the  establishment  of 
the  system. 

7v''>...The  galleries  should  not  be  run  out  to  sxry considerable 
distance  beyond  the  covered-ways,  both  on  account  of  procur- 
ing a  good  circulation  of  air,  and  because  very  advanced  gal- 
leries are  easily  destroyed  by  the  besiegers.  Hie  distance  to 
which  the  galleries  may  extend  should  he  so  much  the  ].  as, 
the  ground  above  them  is  well  protected  by  the  collateral 
works. 

787. ..The  soil  must  be  suitable  for  the  establishment  of  a 

tem;  wet,  marshy  ground,  shifting  sand,  and  hard  rock, 
present  almost  insuperable  obstacles;  whereas,  a  (\vw  firm 
soil,  soft  roek.  or  ordinary  earth  under  a  thin  superstratum  of 
hard  roek,  are  very  favorable  circumstances.  If  the  sub-soil 
is  wet.  but  ]  i  firm  and    dry  superstratum  1  L'  feet    thick 

■bore  the  level  at  which  the  water  collect.-,  mines  may  still  bo 
placed  with  advantage* 

788... Bi  wd<  -  the  above  general  condition*,  then-  are  certain 
•  d  to  in  arranging  the  galleries  and 

chambers. 

The   galleries   should    be   placed    a-  far   below  the   surf: 
practicable,  to  withdraw  them  from  the  effect  of  the  glolw 
com  of  the  'P.  drain   the  galler 

should  h  _ht  inclination,  about  1  50,  toward  the  ditel 

or,  if  the   -round    <}■  .  d    a    hollow  . 

may  he  given  in  that  direction. 


288  mini fc 

7^0. ..The  chambers,  on  the  contrary,  should  he  near  tlio  ?ur- 
face;  by  this  arrangement  the  powder  ia  economized,  and  all 
danger  to  the  galleries  from  the  explosion  avoided;  whilst  the 
object  of  the  minesrwhieh  is  to  destroy  the  enemy's  works, 
can  be  as  fully  attained  by  small  mines  as  large  ones. 

790..-Tij/e  galleries  should  dot  be  placed  nearer  to  each  other 
than  twice  the  line  of  least  resistance  of  the  heaviest  charged 
mines,  and  not  much  less  than  four  times  the  line  of  least 
resistance  of  the  smallest  charges.  This  arrangement  will 
admit  of  a  combination  of  mines  in  two  tiers,  the  line  of  Lead 
resistance  of  the  lower  being  double  that  of  the  upper*  the 
chambers  of  which  may  be  so  arranged  that  the  explosions  of 
one  tier  shall  not  affect  either  the  galleries  or  the  mines  of  the 
other.  Twice  the  line  of  least  resistance  of  the  largest  mines 
is  the  least  distance  that  can  be  allowed  between  the  galleries, 
in  order  that  the  mines  of  the  lowest  tier,  which,  being  placed 
near  one  gallery,  must  destroy  a  part  of  it,  shall  not  injure 
those  parallel  to  it.  By  placing  the  galleries  at  this  least  dis- 
tance apart,  the  branches  for  the  service  of  the  upper  tier  will 
be  as  short  as  possible,  affecting  thus  a  saving  of  time  and 
labor,  and  from  the  same  cause  the  galleries  on  any  one  point 
being  as  many  as  can  be  placed,  there  will  be  the  advantage 
that  some  one  of  the  galleries  will  be  serviceable  should  others 
be  injured  by  explosions. 

791. ..The  galleries  and  branches  for  the  service  of  the  differ- 
ent groups  of  mines,  should  be  Independent  of  each  other,  so 
that  there  may  be  no  confusion  in  the  service,  and  that  no 
group  may  be  rendered  unserviceable  by  the  destruction  of 
the  communications  to  another.  The  same  principle  should 
be  attended  to  in  combining  the  different  groups  of  mine 
chambers/ 

792. ..The  galleries  and  branches  should  never  present  their 
flanks  or  sides  to  the  globes  of  compression  of  the  besiegers. 
This  rule  leads  to  the  rejection  of  enveloping  galleries. 

793. ..The  systems  of  countermines  proposed  by  most  writers 
on  this  branch  of  the  defence  are  generally  of  too  complicated 


MINKS.  289 

a  character  to  admit  of  being  executed  at  a  reasonable  costj  and 
they  require  for  their ■  service  not  only  a  large  amount  of 
powder  but  also  a  great  number  of  miners. 

The  following  arrangement,  based  on  the  general  conditions 
jnst  laid  down,  lias  been  proposed,  to  meet  in  a  simple  and 
satisfactory  manner  the  requisites  of  a  subterranean  defence: 

Parallel  to  the  capital  of  the  demilune,  four  listening  gal- 
leries are  run  out  to  a  distance  of  from  50  to  8<»  yards  beyond 
the  salient  of  the  covered-way.  The  interval  between  these 
galleries  being  twice  the  line  of  least  Msietanee  of  the  heav- 
iest charged  mines.  If  we  take  this  line  at  7  yards,  or  21  feet, 
which  is  about  the  greatest  for  common  mines,  the  interval  of 
the  galleries  will  l»e  K>  yards.  The  dimensions  of  the  listen 
ing  galleries  for  about  the  first  20  yards  may  be  those  of  a 
grand  gallery,  and  the  remaining  part  may  be  a  common  gal- 
lery. These  galleries  will  depart  from  i  transversal  grand 
gallery,  about  <">  yards  from  the  demilune  counterscarp,  which 
will  serve  as  a  communication  between  them,  and  also  as  ft 
depot.  Other  transversals  of  the  size  of  half  gallern 
branches,  will  be  made  at  different  intervals  for  the  purpose 
of  ventilation.  This  group  of  galleries  will  have  their  outlet 
into   the   demilune  ditch   through  two  gallei  leading 

from  each  extremity  of  the  transversal  grand  gallery.  I  i 
flank  tliia  group,  other  listening  galleries  will  extend  obliquely 
outward  from  the  two  outside  parallel  gallera  ]  serve  the 
mines  of  thia  group,  a  ding  bra  ''ill  lead 

from  the  galleries  to  chambers  placed  midway  between  the 
galleries,    having  a  line  of  l<  if  4  yards.     This 

will  place  these  chan  about  s  yarda  from   I  ad- 

jacent   galleries.     Smaller   branches   may  lead,  it'  necessary, 
from  these  last  branches  to  other  groups  of  chambers,  ha 
a  line  of  f  cham- 

bers with  lines  of  lea 

in   juxtaposition    wil  i  roti 

rangemenl    it   will   be  readil; 
i 


290  mi\ 

Bxplpsions  of  the  mines  of  one  group  will  destroy  the  branches 
and  galleries  which  tead  bo  them,  without  injuring  those  6f 
other  l:t« >u]>>.  The  object  of  this  disposition  is  to  blow  up  by 
repeated  explosions  the  ground  over  which  the  enemy  must 
approach  apon  the  demilune  salient  place  ef  arras. 

794...For  the  defence  of  the  other  portions  of  the  glac 
the  demilune  covered-way.  a  counterscarp  gallery  of  the  di- 
mensions of  a  grand  gallery  is  placed  between  the  two  traver- 
ses next  to  the  reentering  place  of  arms ;  a  listening  gallery 
extends  from  one- extremity  of  tin's  gallery  in  an  obliqu^  di- 
rection outward,  and  nearly  parallel  to  the  long  branch  of  the 
covered-way    CFesf    hetween    the    two    traverses,  to  within  BO 

yards  of  the  foregoing  arrangement.     Other  listening  galled 

ies,  placed  l.">  yards  apart,  run  out  from  the  main  one,  about 
20  yards,  to  menace  every  point  i>i'  the  glacis  that  can  tie  oc- 
cupied by  the  beseiger's  works.  The  groups  of  mines  for 
these  galleries  may  be  arranged  like  those  of  the  combination 
in  advance  of  the  demilune  salient  place  of  arms.  The  coun- 
terscarp  gallery  should  have  two  outlets  in  the  demilune  ditch ; 
hut  as  these  might  compromise  the  safety  of  the  whole 
arrangement,  should  the  besiegers  attack  the  covered-way  by 
Storm,  they  must  be  walled  up  when  the  third  parallel  is  com- 
pleted, and  the  communication  with  the  galleries  then  kept  up 
by  a  gallery  leading  to  the  main  ditch.  To  supply  the  main 
listening  gallery  of  this  group  with  air,  a  branch  should  lead 
to  it  from  a  point  of  the  demilune  counterscarp  under  the  tra- 
verse next  to  the  one  of  the  salient  place  of  arms. 

iT9 5... Groups  of  gaUeriefi  and  mini's,  similar  to  the  one  in 
front  of  the  demilune  salient  place  of  arms,  may  be  arranged 
for  the  defence  of  the  bastion   salient   place   of  arms.      And   a 

gallery,  leading  from  the  counterscarp  oi  the  main  ditch,  may 
he  made  for  the  service  of  a  group  for  the  defence  of  the  glacis 
of  the  reentering  place  of  arms. 
7'j<;...To  defend  the  breaches  made  in  the  demilune  and  its 

reddidit,  a  gallery  may  he  made  under  the  ditch  of  the  re- 
doubt, having  its  outlet  in  the  main   ditch;  this  gallery  may 


MINIS.  201 

divide  into  two  branches,  one  leading  under  the  demilune 
breach,  the  other  under  thai  of  the  redoubt.  Ascending 
branches  may  be  made  from  the  gallery  leading  to  the  demi- 
lune breach,  for  the  service  of  agroupof  mines  to  blow  up 
the  demilune  terreplein. 

7i»7... Finally,  if  the  bastions  arc  arranged  with  interior  re- 
trenchments, a  disposition  similar  to  the  one  made  for  the 
defence  of  the  demilune  may  also  be  made  for  the  defence  of 
the  bastion  breach. 

T'.,v....\-  the  air  in  the  galleries  of  mines  is  liable  to  become 
foul  from  various  causes;  some  mechanical  contrivances  and 
chemical  methods,  by  whioh  the  vitiated  air  can  be  removed 
ami  fresh  air  introduced,  have  to  be  resorted  to  for  the  pur- 
pose  of  enabling  the  miner.-  to  circulate  through  them  with 
safety.  Air  pumps,  bellows,  and  artificial  drafts  procured  by 
kindling  afire  at  one  of  the  outlets  of  a  system  of  galleries,  are 
the  ordinary  expedients  by  which  this  object  i*.  attalried. 

799.. .The  great  pecuniary  outlay  requisite  in  establishing  a 
system  of  permanent  galleries,  besides  the  large  oorps  o€  ex- 
perienced miners  and  the  extra  provision  of  powder  demanded 
for  their  efficient  service,  when  the  system  embraces  any  con- 
siderable extent   of    surface,  has   led   engineers   to   eon 

whether  the  end    proposed    by  Mil  it  '■rranean    I  defence 

might  not  be  attained  by  some  more  simple  expedients,  since 
the  application  of  galvanic  current!  to  exploding  mines,  and 
the  facilities  which  it  affords  to  effect  this  at  very  considerable 
distances,  it  has  been  propose  d  to  substitute  ;-  ■  for 

galleries,  placing  them  in  positions  m  .Me  to  attain  the 

>rks.     Tl  :•  ..f 

permanency,  may  be  lined  with  masonry,  and  r< 
or  iron  cover  which  may  be  eonoealed  from  view  I  it  pla 
it  several  feet   below  th<  When  wanted  for 

the  shafts  are  charge  d  and  tamped  in  the  usual  i  .  and 

connected   with   a  galvanic   battery  by 
ductors,  laid  sufficiently  far  b< 

be  without  tl 

ccrdents. 


292  ATTACK   AND   DEFENCE    OF    l'I  KMAMNT    WOBX8. 


ATTACK  AXD  DEFEXCE  OF  PERMAXEXT  WORKS. 


FRENCH  MATERIALS. 

1... Under  this  head  arc  comprised  the  materials  used  by 
tin-  besiegers  for  revetemenis  and  covers  against  the  fire  of  the 
defences. 

Fa-,  im:-.  These  are  usually  made  18'  long,  and  9"  in 
diameter,  and  are  afterward  cut  into  suitable  Lengths  for  the 
purposes  to  which  they  are  to  be  applied. 

Pickets.  Those  used  for  securing  fascines  are  from  2'  to  4' 
long,  and  from  1^"  to  If"  thick ;  those  for  setting  out  or  tracing 
the  works  are  18"  long  and  1"  diameter. 

Sai'-i-a<;<>'js.  These*  are  made,  like  fascines,  of  straight  brush- 
wood at  least  1"  in  diameter.  They  are  -'  '•'"  long,  and  9"  in 
diameter.  The  centre  stake  should  he  from  H"  to  2"  in  diame- 
ter, and  project  \)"  beyond  one  end  of  the  Bap-fagot;  this  pro- 
jecting portion  is  sharpened,  to  enable  the  sap-fagot  to  be 
planted  firmly  in  the  ground  in  an  upright  position* 

Gajjions.  The  exterior  diameter  of  these  is  2',  and  the 
height  of  watling  is  2'  9".  They  arc  made  with  seven  or  nine 
stakes,  which  project  6"  above  the  watling  at  top,  and  ap- 
pointed. 

At  the  siege  of  Sebastopol,  the  want  of  brush-wood  for  the 
watling  of  gabions  led  to  the  introduction  of  the  common 
hoop-iron,  fof  this  purpose,  which  had  served  to  secure  the 
bales  of  hay.  The  number  of  pickets  employed  fo?  each  gabion 
was  usually  thirteen.  It  was  found  that  these  gabions  could 
be  constructed  more  readily  than  the  ordinary  kind;  that  they 
were  not  much  heavier,  more  durable,  and  in  all  respects  as 
serviceable.     Since  then,  it  has  beeu  proposed  to  use  simple 


ATTACK    ANIi    DEFENCE   OF    riKM.Wl.vi    WORKS. 

Bheet-iron  cylinders,  of  suitable  dimensions,  instead  of  the 
brush-wood  gabion.  For  this  purpose,  rectangular  sheets  of 
iron,  of  suitable  dimensions  to  form  cylinders  of  the  same 
height  and  diameter  as  the  ordinary  gabion,  arc  prepare/i* 
with  three  or  four  holes  flinched  near  and  parallel  to  the 
shorter  sides  of  the  sheet  to  secure  these  ends  with  wire  when 
the  sheet  is  bent  into  the  cylindrical  shape.  Besides  tie 
tw<i  other  holes  of  larger  size  are  punched  toward  the  central 
portion  of  the  sheet,  ao  as  to  be  diametrically  opposite  when 
the  cylinder  is  formed,  to  receive  a  picket  passed  through 
them- which  serves  as  a  handle  in  carrying  the  gabion.  The 
advantages  of  this  description  of  gabion  are  greater  strength, 
lightness  and  durability  than  either  of  the  others;  offering 
great  facility  for  dbtant  transportation,  and  resisting  bettor 
the  blast  of  guns  when  used  for  revetting  the  cheeks  of  embra- 
sures, 

Sap-boi^j  i;-.  This  i.-  a  large  gabion,  7'  <i"  in  length,  and  V 
4"  exterior  diameter.  It  requires  (or  its  construction  fifteen 
■takes,  each  from  14/'  to  2"  in  diameter.  After  it  is  completed, 
it  is  stuffed  compactly  with  fascines  7'  <;"  long.  The  sap-roller 
is  sometimes  made  df  t*vo  concentric  gabions,  the  diameter  of 
the  smaller  2*  *>".  The  space  between  the  two  is  compe 
stuffed  with  i 

S.\M-i;\o-.  Tie-  mu  d-bag,  for  the  revetement  of  battel 
when  empty  and  laid  flat,  is  2*  s"  Long  and  1'  4"  wide  :  r 
used  in  the  construction  of  the  trench*  i  are  _'  long,  l_"  « 

r.uM>\oi -i  k  wii -.    These  frames,  Pi.  to,  Fig.   I,  are  com- 
posed of  two  uprights,  or  stanch  cantling, 
<;"  long,  and  pointed  at  both  end*;  and  two  horizontal  pit 
of  the  same  Bised  scantlii  i 
piea              tr-lied  npon  I                             12"  from  i  a<  b  • 
The  width  of  the  frame  from  out  to  out  is  3'  \" :  the   • 
between  the  horizontal  pi<  <■<  -  from  onl  to 

An  auxiliary  ■' 
used  in  |  •  be  blindag*  fran  • 


204  ATTACK    AND   DEFENCE   OF   PERMANENT   WOHK&. 

Ctai.i.i'ky-i  i:  \mi<.     The  arrangement  and  dimensions  of  these 
are  the  same  as  those  used  in  mining. 


TRENCHES. 

2. ..The  term  f/v/ir/i  is  applied  to  an  excavation  or  ditch  made 
by  the  besiegers,  by  means  of  "which",  and  of  the  earth  thrown 
from  it,  they  are  enabled  to  obtain  speedy  cover  from  the  tire 
of  the  defence's,  and  to  approach  them  with  security. 

Trenches  are  divided  into  two  principal  classes — the  paral- 
lels and  the  approaches.  The  parallels  are  designed  as  stations 
for  troops  to  guard  the  trenches,  and  the  workmen  employed 
in  their  execution,  from  the  sorties  of  the  garrison.  The  ap- 
proaches serve  simply  as  covered  communications  which  lead 
to  the  parallels,  and  toward  the  points  of  the  defences  upon 
which  the  attack  of  the  besiegers  is  directed. 

The  general  direction  of  the  parallels  is  parallel  to,  or  con- 
centric with,  the  line  connecting  the  most  salient  points  of  that 
portion  of  the  defences  attacked.  The  approaches  are  run  in 
a  zig-zag,  or  in  a  straight  line,  upon  some  or  all  of  these  points. 

SL.The  trenches  of  the  parallels,  P1M0,  Figs.  3,  4,  5,  6,  re- 
ceive a  width  at  bottom  of  10' ;  their  depth  in  front  is  3',  and 
in  rear  3'  0".  '  Two  steps,  each  18"  high  and  IS"  wide,  lead 
from  the  bottom  of  the  trench,  on  the  front  side  to  the  natural 
ground.  The  reverse  of  the  trench  receives  a  slope  of  45°,  or 
else,  is  also  cut  into  two  steps.  The  steps  in  front  are  alone 
revetted  with  fascines.  The  trenches  of  the  approaches,  PI. 
10,  Figs.  7,  8,  are  8'  wide  at  bottom,  .".'  6"  deep  in  front,  and  1' 
at  the  rear.  The  reverse  receives  a  slope  of  45°.  The  front  is 
usually  made  with  a  slope  of  2'  base. 

The  earth  from  the  trench  is  thrown  to  the  front  to  form  a 
parapet.  The  general  height  of  this  parapet  is  nearly  5',  its 
width  at  the  base  about  18'. 

4...SiMPLK  TitK.veii.  AVhen  the  parapet  is  formed  of  earth 
alone,  Figs.  3,  4,  7,  the  trench  is  termed  a  simple  firendh.  In 
this  case  the  earth  of  the  parapet  is  allowed  to  take  its  natural 


ATTACK    AN1>    IM.HVI      OF     I'lKMAM.VI     WOBEB.  295 

slope  on  the  side  toward  the  trench.  Xhostep,  orberm,  of  lv", 
between  the  fodl  of  the  parapet  and  the  trench  in  the  parallels 
serves  as  a  banquette. 

Portions  of  the  parallels,  Figs.  4,  fi,  from  20  to  30  yards  in 
length,  are  arranged  with  steps,  revetted  with  fascines,  lead- 
ing from  the  trench  over  the  parapet,  to  enable  the  troops  in 
tlic  parallel  to  debouch  from  it  against  a  sortie. 

The  direction  of  the  trench  is  laid  out  by  pickets,  connected 
Ox  white  tape,  which  is  marked  off  into  Lengths  of  6'  by  short 
pieces  attached  to  it.  The  trench  is  executed  by  Soldiers  of 
the  line  ;  each  man  being  furnished  with  a  pick  and  shovel, 
with  which  he  excavates  0'  in  length  of  the  trench,  and  as 
much  of  it    to   the   rear  as  may   he   assigned    to   the    relief,    or 

working  party,  to  which  he  belongs.     After  the  trench  has 

received  its  general  width  and  depth,  the  slopes  and  ?>tcps  are 
finished  off  with  the  asnstance  and  under  the  direction  of  the 
engineer  troops. 

.V..I'mi.\<,  Sap.  AVhen  the  trenches  have  Leen  pur-hed  for- 
ward to  within  destructive  range  of  case  shot,  the  construc- 
tion by  the  simple  trench  has  to  l.e  abandoned,  and  one  which 
will  afford  more  spei -dy  shelto  r  resorted  to.  This  is  effected, 
5,  v.  by  placing  ;i  row  of  ordinary  gabions  in  juxtaposi- 
tion, along  the  direction  of  the  trench  ;  these  being  filled  with 
tlie  earth  from  the  trench,  the  parapet  i>  completed  by  throw- 
ing the  remaining  earth  over  and  beyond    them.     This  pw 

rmed    the    living    sap,    from    the    rapidity  with  which  the 
Work  i>  done.      It.  also,  U  executed  by  troops  of  the  1; 
man  bringing  two  gabions  on  the  ground,  which  he  i>  requi 
1.  and  .  the  portion  of  the  trench,  in 

rear  of  them,  assigned  to  the  relief  to  which  he  belong 
requisite  height  to  tin-  parapet  either  by  heaping 

the  earth  ab<  '  by  plac 

dinary  :..  ipon    tin  -.  two  being  in  the    botl 

cour-'   and  th(     '        cm  top,  and  I 
inc. 

In  | 


296  ATTACK    AND    DKVEOffCB    OF    PF.UMANT.XT    WORKS. 

quantity  to  afford  a  speedy  cover,  as  in  a  shallow  stratum  of 
soil  on  rock,  etc.  two  rows  of  gabions;  placed  in  juxtaposition, 
may  be  used  tor  the  flying  sap. 

The  troops  tor  constructing  both  this  and  the  simple  trench 
aiv  divided  into  three  parties,  or  relict's.  The  first* digs  the 
trench  to  the  requisite  depth  and  to  the  width  of  .V;  the  second 
widens  it  4'  G";  the  third  tinislies  what  remains,  giving  the 
requisite  slopes  to  the  front  and  rear. 

EtsMASK.  The  dimensions  and  form  given  to  the  profiles  of 
the  parallels  and  hovanx  in  the  preceding  paragraphs  are  those 
used  in  our  own  and  the  English  sapper  practice.  The  French 
allow  usually  3'  3"  for  the  uniform  depths  of  both,  and  4'  3" 
for  the  height  of  parapet.  This  gives  a  cover  of  7'  G"  in  the 
trench,  which  would  seem  ample,  whilst  it  gives  the  parapet 
a  more  suitable  height  for  the  convenient  delivery  of  the  fire, 
if  the  troops  stationed  in  the  parallels  are  called  upon  to  repel 
a  sortie  in  this  way. 

G...Full  Sap.  The  full  sap,  Figs.  9,  10,  11,  is  resorted  to 
when  the  fire  becomes  so  destructive  that  the  living  sap  can- 
not be  used.  The  trench  is  opened  and  pushed  forward  l>y 
engineer  troops  alone ;  for  this  purpose  a  working  party, 
termed' a. brigade,  of  eight  sappers  is  requisite.  The  brigade 
is  divided  into  two  equal  sections;  the  sappers  of  the  first 
section  dig  the  trench,  and  arc  numbered  from  1  to  4,  No.  1 
leading.  The  other  four  arc  termed  assistants;  they  bring 
forward  the  materials,  and  assist  the  first  section  in  all  the 
necessary  operations. 

The  leading  sapper,  No.  1,  is  provided  with  a  pick  and 
shovel,  and  wears  a  musket-proof  helmet  and  cuirass;  he 
works  on  his  knees,  being  covered,  on  his  side  toward  the  de- 
fences, by  the  parapet  of  the  trench,  from  which  he  debouches, 
and  In  front  by  a  sap-roller,  which  is  placed  perpendicular 
to  the  line  of  direction  on  which  he  is  to  work,  and  rest* 
auaiust  the  gabion  he  is  filling,  covering  it  one  foot.  The  por- 
tion of  the  sap  which  he  digs  is  21"  wide  at  the  top  and  L;l" 
deep  ;  it  receives  a  slope  of  4  perpendicular  to  1  base  on  the 


ATTACK    AND    DKFI.XCI     OF    ITKMANTWT    WORK.  207 

front,  and  is  vertical  in  the  rear;  and  its  length  is  .V.  Softool] 
as  this  portion  is  finished.  No.  l\  who  is  projected  in  all 
like  No.  1,  commences  to  widen  and  deepen  the  trench  s"  at 
the  point  from  winch  No;  1  started,  and  follows  on  after  No. 
1,  keeping  alsravs  5'  in  his  rear.  When  X<>.  9  has  pu.-hed  for- 
ward .">'.  No.  3  commences  and  enlarges  the  trench  in  each  di- 
rection  7";  he  follow*  on  also  5'  in  rear  of  Ne.  8j  hut  as  the 
work  thrown  up  by  the  sappers  preceding  him  affords  pretty 
good  cover,  lie  can  work  standing,  taking  the  precaution  to 
bend  forward  for  gr  curity.      Finally,    No;    4    bej 

when  No.  3  lias  got  on  .V,  and  deepens  and  widens  7".  As  he 
is  well  covered,  he  can  work  in  an  unconstrained  posture. 

lea  the  shelter  given  by  the  gabions;  as  they  are  suc- 

welv  filled,    and    the    sap-roller,  the  further   precaution   is 

taken  of  •'driving  sap-1  Long  the  berm,  a1   the  junction  of 

the  gabions;  these  are  successively  removed  as  they  are  no 

_  i-  requisite.     The  trench  fascines  are   placed   upon   the 

gabions    by  the    assistants,   and    the    remainder    of  the    trench 

completed  by  working  parties  of  the  line,  so  soon  as  the 
brigade  of  sappers  have  proceeded  far  enough  for  tin.'  others 
to  commence  without  hindrance. 

7...1)<Tm.i  Bajb.  This  sap,  Figs,  L2,  13,  consi-t.-  of  two 
h«-ad.-  of  sap  pushed  forward  by  two  brigades  working  abreast 
It-  object   i.-  to  form  a  trench   in  a  position  •  both 

sides  to  fire.    The  head  of  the  sap  is  covered  by  two  sap- 
roller.-   placed  end  to  end;  a  bag  of  wool,  or  a  short  .-ap-roller, 
being   placed  at   their  junction,  for   additional    security.'    . 
distance  between  the  two  rows  of  gabions  is   1-'.  arth 

between  the  two  line.-  of  |gp  fa  removed  by  the  usual 
parties,  a-  in  the  prei 
v..  1 1  i :  Sap.  <>f  full  i 

1  J,  pushed  forward  in  a 

temporary  cover  on  the  r<  verse  of  th< 
filled  with  sand-bags.      I 
gabions,  in  1 
Log  in  front  this  interval  Iron  .re. 


298  ATTACK     AM»    I'll  I.N.I.    Q»     I'IKMAM.M     W0SXB. 

9...Di:fji.i.mi:n t  ok  Tki  .wins.  The  position  given  to  the  lines 
of  the  parallel,  and  the  dimensions  adopted  for  its  trench  and 
parapet,  give  ample  cover  to  the  troops  in  it  from  the  plung- 
i n g  fire  of  works  having  anything  like  the  usual  command. 
But  in  the  zig-zag  approaches,' or  boyaux,  as  tlie  line  of  the 
trench  has  to  be  directed  toward  the  defences,  it  is  necessary 
cither  to  defile  the  trench,  by  giving  it  a  direction  such  that 
the  lire,  coming  over  its  parapet,  will  not  have  a  plunge  sutfr- 
cicnt  to  attain  a  man  standing  in  the  reverse  of  it,  or,  when 
this  cannot  be  done,  by  placing  traverses  along  the  line  to  be 
covered,  Which  shall  effect  the  proposed  end. 

In  the  usual  cases  of  practice,  the  ground  on  which  the  ap- 
proaches are  run  will  be  more  or  less  uneven,  and  this  in- 
equality of  surface,  if  quite  appreciable,  will  demand  a  corres- 
ponding variation  in  the  line  of  direction  of  an  approach, 
where  its  defilement  is  to  be  effected  by  the  position  given  to 
it  with  respect  to  the  point  from  which  it  may  be  attained  by 
the  enemy's  fire.  In  most  cases,  however,  each  portion  of  the 
line  of  the  trench,  corresponding  to  the  changes  in  the  surface, 
may,  without  any  very  great  error,  be  regarded  as  lying  either 
on  a  horizontal,  or  an  inclined  plane;  and,  in  the  latter  ease, 
the  plane  may  either  rise  toward  the  dangerous  point  or 
descend  in  the  same  direction;  there  will,  therefore,  arise 
three  cases  of  defilement,  according  to  the  position  of  the 
plane  on  which  the  trench  is  run  with  respect  to  the  dangerous 
point. 

To  illustrate  these  cases,  let  the  approach  to  be  defiled,  be  a 
trench  constructed  with  the  Hying  sap.  Now,  whether  the 
ground  be  horizontal  or  inclined,  the  relative  position  of  the 
lines  of  the  profile  of  the  approach  should  be  preserved  as 
nearly  as  practicable.  The  vertical  height  of  the  top  of  the 
parapet — supposing  the  latter  no  higher  than  the  top  fascine — 
above  the  bottom  of  the  trench,  at  the  reverse  side,  Figs.  15, 
16,  17,  will  then  be  8'  3";  and  the  horizontal  distance  between 
the  same  points  12'.  Now,  in  order  that  a  man  standing  at 
the  reverse  of  the  trench  may  be  secure,  the  line  of  fire  of  the 


ATTACK   AXD   DBFEITOE'OP    PERMANENT    WOH  291) 

enemy  should  not  have  a  greater  plunge  than  6*  f>"  above  the 
bottom  ofthe  trench  at  this  point.  Tin's  will  limit  the  inclina- 
tion of  the  line  of  fire  to  the  horizontal  dfawn  through  the 
top- of  the  parapet  to  about  1  perpendicular  to  7  bate,  or  an 

angle  of  1-fi  It  will  readily  be  Been  from  this  that  the.  line 
of  the  trench  must  nol  be  run  so  near  the  dangerous  point 
that  the  line  of  tire  from  it,  passing  through  the  top  point  of 
the  parapet,  and  in  the  direction  ofthe  profile  of  the  trench — 
that  LB,  in  a  vertical  plane  containing  the  dangerous  point,  and 
perpendicular  to  the  horizontal  projection  of  the  line  of  the 
trench — shall  make  a  greater  angle  than  1-7;  and  that,  when 
the  line  ofthe  trench  satisfies  this  condition,  it  will  be  defiled 
by  its  position. 

To  Fi\i»  Tin  DsrtLBB  Position  op  a  TWekch  oh  Bfoattbir* 
tal  Groino.  Le4  I>.  Pig.  Is.  be  the  point  of  departure  of 
an  approach  leading  from  a  parallel,  and  C  the  most  dan- 
gerous point  of  the  defences  for  this  approach,  the  height  of 
which  above  the  parapet  ofthe  approach  is  known.  It  is  evi- 
dent, from  what  has  just  been  laid  down,  if  the  approach  were 
continued  on  beyond  the  point  C\  and  a  line  with  an  inclina- 
tion of  1-7  were  drawn  from  Q  perpendicular  to  the  direction 
ofthe  approach  and  through  the  top  of  its  parapet,  that  a  man 
Standing  at  the  reverse  of  the  bottom  of  the  trench  would  not 

be  attained  by  this  fire  i  but  m  the  top  of  the  parapet,  or  in- 
terior creal  of  the  approach,  is  horizontal,  and  the  reverse  of 

the  bottom  of  the  trench  is  parallel   to  it.  it  is  farther   evident 

that  the  plane  which   passes  through  the  point  0 and  the  in- 
terior crest  of  the  approach,  will  pass  at  the  same  height  ab 
e\. tv  point  of  the   n  I  the  bottom  of  the  trench  that 

me  of  1-7,  through  ('.<]■■  the  point  < < . 

line  lies  in  the  plane  ;   it.  tie-:  at.    if  the    ] 

defiled,  i  ther  point  along  the  i  rich 

will  also  be  defile  L.     To  c  ■  itract  the  position  of  the  Lift    /' 

tiv.  w  Lth  a  I.e.     i-  •    |  .  .     '      -  vertical  he 


300  ATTACK    AMi    DEFENCE   OF    l'l.KMAXKNT   WORKS. 

above  the  parapet  of  the  approach,  an  arc  of  a  circle,  the  tan- 
gent to  this  arc  from  1>  will  he  the  required  position* 

.\..ii.  Iii  Fxgi  Is.  the  dangerous  point,  C.  is  18'  above  the 
horizontal  plane  of  the  trench.  The  reference  of  this  plane 
being  (0),  that  of  the  point  6' is  (18.0),  and  that  of  the  inte- 
rior crest  of  the  approach  ii  1 4;25  i.  Tin-  reference  of  the  point 
a  is  (11.0);  the  declivity  of  the  glacis  planes  1-21. 

10. ..To  11.NI>  illl  .1)1. HI. in  I'wHTloN  oK  AN  APPEOACB  o\  Ix- 
n.i.NED  Grouni'.  l.ci.  Fig.  IS,  two  planes  of  a  glacis  inter- 
tcrseeting  in  a  ridge,  a  J,  one  of  the  planes  rising  in  the  direc- 
tion of  the  dangerous  point  C\  and  the  other  falling  toward  ir, 
he  taken  as  the  ground  on  which  the  trenches  are  to  be  run  ; 
and  let  A,  at  the  foot  of  the  plane  which  ascends  towards  6", 
be  the  point  of  departure  of  the  approach.  Now,  the  plane 
being  produced  toward  6' may  either  pass  above  it,  through  it, 
or  below  it ;  in  either  of  the  two  first  positions  it  is  evident,  if 
the  interior  crest  of  the  approach  were  directed  on  the  point 
6',  that  the  trench  would  be  defiled;  for  no  line  of  tire  from 
C  would,  in  cither  of  these  cases,  have  a  plunge  into  the 
trench,  and  the  same  would  hold  true  if  the  plane  produced 
passed  at  a  distance  below  it  just  equal  to  the  height  of  para- 
pet of  the  approach.  In  either  of  these  cases,  therefore,  to 
defile  the  trench,  it  will  only  be  necessary  to  direct  its  interior 
crest  on  the  dangerous  point,  and  this  direction  may  be  kept 
until  the  approach  strikes  the  ridge  at  B. 

11. ..At  this  point,  as  the  plane  of  the  glacis  on  which  the 
prolonged  branch  of  the  trench  is  to  be  run  descends  toward 
C,  and  is  seen  in  reverse  by  its  fire,  it  will  be  necessary  to 
change  the  direction  of  this  branch  so  as  to  withdraw  it  from 
the  plunging  fire  from  ('.  This  will  be  effected  by  giving  this 
branch  a  direction  such  that  a  line  of  fire  from  O,  having  an 
inclination  of  1-7,  ami  being  contained  in  the  profile  plane  of 
the  trench  which  passes  through  c7,  shall  clear  the  head  of  a 
man  standing  in  the  trench  at  the  reverse  side;  and  this  will 
be  the  case  if  this  line  of  1-7  passes  through  the  interior  crest 
of  the  parapet  and  6'  0"  above  the  bottom  of  the  trench  at  the 


ATTACK    AND   DEI- 1  \<  B    OF    IM  KMAMM     WOE  301 

vcvorso.  It  is  evident,  in  die  first  place,  tli.it  this  will  be  true 
for  the  profile  plane  through  C.  Now,  since  the  line  of  the] 
interior  crest  and  the  line  of  1-7  intersect,  they  will  determine 
a  plane  which  passes  through  (\  and  in  which  all  the  lines  of 
fire  from.  ('  which  strike  the  interior  crest  are  contained.  As 
the  reverse  line  of  the  hottoin  of  the  trench  is  parallel  to  the. 
interior  crest,  and  as  the  plane  of  fire  in  (]iie>t ion  passed  ;it  d' 
c,"  above  that  point  of  the  reverse  line  of  the  hottom  which  is 
contained  in  the  profile  plane  through  C,  it  follows  that,  this 
•lane  also  passes  at  G' 0"  above  every  other  point  of  this  re- 
ver.-e  Line.  :nid.  therefore,  that  the  direction  of  the  trench 
which  fulfils  this  condition  will  be  defiled  throughout  from  the 
fire  coming  from  C. 

onstruct  this  position,  let  the  point  Cbe  taken  as  the 
vertex  of  a  right  COhe,  the  elements  of  which  make  an  angle  of 
1-7  with  its  base.  The  line  of  fire  of  1-7  will  be  an  element  of 
this  cone.  If  the  com-  be  intersected  by  a  plane  parallel  to 
the  one  on  which  the  approach  is  run.  and  at  a  distance  above 
it  equal  to  the  height  of  the  parapet,  the  interior  crest  of  the 
approach  must  intersect  the  curve  cut  from  the  cone  by  this 
place  ;  and.  to  satisfy  the  conditions  imposed,  the  point  of  in- 

Ctiton  must  he  where    the  projection  of  the  element  of  the 

cone  is  perpendicular  to  that  of  the  interior  crest) 
the  relative  positions  in  projection  of  the  line  of  tire  of  1-7  and 
of  the  approach.     To  construct  the  projection  of  the  curve  cut 
from  tic  cue.  it  will  only  bt  try  to  intersect  the  i 

and  plane  by  equidistant  horizontal  planes,  and  to  find  the  pro- 
ions  of  tin   corn  spending  point.-  of  ml  n  of  the 
cut  from  the  two  surfaces  by  tin  se  plain  -.    To  find  ti 
tion  of  the  approach,  join  the  point  of  it>  departure .  /»'.  with 

ad  oh  this  line  describe  a  semicircle  :  the  p.. 
this  semicircle  cuts  the  projection  of  the  curve  cut  from 
ie  required  direction,  />'  T.  of  the  approa 
A  lik<   e,  :  struction  \\  onld  : 
on  an  osc<  riding  plane  pas*  - 


302  attack    ani>  DJFENCE  off  im'km  \m:n  I  WOBX& 

tance  than  the  height  of  the  parapet  below  the  dangerous 
point; 

12...I1  will  be  noted  from  what  precedes  that  the  approach 
is  never  directed  within  a  dangerous  point  ;  for  the  obvious 
on  tliat.  it'  so  placed,  it  would  he  exposed  to  reverse  fire 
from  die  point  If  it  should  happen  that  the  direction  ]>  X. 
found  tor  the  approach  in  the  preceding  ease,  would  bring  its 
prolongation  within  a  dangerous  point.  (\  on  the  Left  of  the 
ridge*  toward  which  tin-  plane  ascends,  it  would  then  bem 
saty  to  change  the  direction  B  X  to  that  of  C  B  X\  and.  as 
this  would  expose  the  trench  to  a  plunging  lire  from  Q  it  will 
be  farther  requisite  either  to  deepen  the  trench,  or  to  raise  the 
parapet  higher,  to  cover  the  reverse  from  this  plunge. 

1".... It  will  he  farther  noted  that,  at  the  point  of  departure 
of  an  approach  from  a  parallel,  there  will  he  a  portion  of  the 
parallel,  0  j>  y.  in  the  rear  of  the  trench,  which  will  not  he  fully 
covered  l>y  the  parapet  of  the  approach.  This  portion  will  be 
limited  hv  the  line  of  tire  from  17  through  0,  where  the  reverse 
of  the  approach  cuts  the  interior  crest  of  the  parallel;  and  l.v 
the  reverse  prolonged  to  <j.  To  secure  this  portion,  either  the 
Wench  of  the  parallel  naasl  be  deepened  or  that  part  of  the  par- 
apet of  the  approach  be  raised,  which  is  intercepted  hetween 
the  lines  of  lire  from  C  on  j>  and  <y. 

14... I  )i:I']li:mi:nt  i:v  Tkavkksks.  When  the  defilement  can- 
not he  effected  by  the  position  given  to  the  trench,  resort  must 
be  had  to  traverses.  Two  cases  present  themselves  under  this 
head  :  one  in  which  the  reverse  of  the  trench  is  exposed  to  a 
very  slant  lire;  the  other  in  which  the  trench  is  pushed  for- 
ward hetween  two  dangerous  points,  and  is,  at  the  same  time, 
exposed  to  an  enfilading  lire. 

15. ..In  the  first  case.  Fi^.  19,  the  trench  is  carried  forward 
by  means  of  the  half-double  sap.  So  soon  as  the  head  of  the 
sap  has  been  advanced  the  length  of  twelve  gabions  beyond 
No.  4,  a  short  end  of  sap,  termed  a  winy  traverse^  is  com- 
menced in  a  direction  perpendicular  to  that  of  the  trench,  and 
run  out  until  it  intercepts  the  line  of  lire  upon  the  point  of'de- 


ATTACK     AM»     l-l  I  I  M    I      01      II  KMAM'N'I      WOBKS.  303 

partnre  at  the  distance  of  twelve  gabions  in  it-  rear.  When 
this  end  of  Bap  Id  completed,  the  provisional  parapel  in  its 
roar  can  be  taken  down  ami  the  trench  enlarged  to  its  proper 
width.  In  tin's  way  the  trench  is  successively  pushed  forward 
and  enlarged,  until  a  position  had  been  reached  Where  it  be- 
comes necessary  to  place  a  traverse  to  cover  the  trench  from 
both  enfilading  and  rovrrtr  views.  These  traverses,  .1.  .1. 
made  by  changing  the  direction  of  the  trench  perpendicular  to 
that  of  the  original  line,  and  continuing  in  this  new  direction, 
by  the  full  sap,  the  requisite  length  of  the  traverse  :  the  origi- 
nal direction  is  then  resumed,  and  continued,  by  the  half*double 
sap,  a  sufficient  distance  to  leave  room  For  the  width  oil  the 
traverse  ami  a  trench  of  double  sap ;  another  rectangular  turn 
is  then  made,  by  the  doable  Bap,  hack  to  the  line  of  gabions  of 
the  original  tn  nch,  and  the  original  direction  is  again  taken 
up  and  carried  forward  by  the  half*dottbl<   Bap. 

The  ti;.  I.J.  are  Bey%n  gabions,  or  about  14'  in  width. 

Their  length  will  depend  on  the  position  of  the  dangerous  point, 
but  the\  Ion  made  over  9&  in  length.     Their  distance 

apart  will  also  depend  on  the  command  of  the  dangerous  point. 
The  portion  of  trench  between  any  two  traverses  must  he  per- 
fectly covered  by  the  advanced  travel---.  A-  i  practical  rule, 
the  traverses  are  not  placed  farther  than  26  or  80  yard-  apart. 

The  portion  of  the  trench,  II.  in  rear  of  the  end  of  the  trav- 
.  >vered  by  extending  sufficiently  far  to  the  rear  of  it  an 
end  <>f  trench,  ( '.  fori  |  the  line 

of  dan)  fire. 

!■;... In  1  90*  the  trench,  ^,ie  carried fi 

ward  by  the  double  sap,  until  the  point  of  departui 
about  being  expose  d  to  the  fire  cominj 
a  chfl  .'...- 

full  sap,  to  the  right 

about  ti:'  .  when   the  original  i  .  />.  bi 

doub  lumed.     A    i 

made  both  to  th' 
direction,  by  the  full 


304  ATTACK    ANT*   DEFECT  V.    OF    IT.KMAMNT    WORKS. 

or  fourteen  gabions.  Then,  from  the  extremities  of  these 
hranche.-,  a  direction  parallel  to  tin1  Original  is  taken  up  by  the 
double  sap.  and  pu^ied  on  until  the  point  of  departure  is  about 
being  etposed,  when  a  change  of  direction  is  made  at  right 

angles  by  the!  full  sap.  and  the  two  branches  are  united  on  the 
original  direction,  A]  which  is  resumed  by  the  double  sap. 

17...Ti:r.xcii  C\\\Ai.u:ii.  This  work  consists  of  a  parapet 
raised  on  a  mound  of  earth,  for  the   purpose  of  obtaining  a 

plunging  tire  on  the  covered-way.  The  mound  should,  in  all 
ca>cs,  be  raised  so  high  that  the  cavalier  will  have  a  command 
of -i-^  feet  over  the  crest  of  the  covered-way.  The  position  of  the 
cavalier  is  shown  in  PL  A,  Fig.  5.  When  the  trenches  are  ad- 
vanced liv  the  full  sap  nearly  within  reach  of  grenades  thrown 
by  hand,  or  about  30  yards  from  the  salient,  <i<  of  the  covered- 
way,  a  circular  -portion  of  trench,  b  c,  is  formed,  to  embrace 
the  production  of  the  crests  of  the  salient;  from  the  extremi- 
ties of  this  circular  portion  the  sap  is  run  perpendicular  to  the 
direction  of  the  crests,  to  a  distance,  c  d,  of  about  8  or  12 
yards,  so  as  to  enfilade  the  covered-way;  at  the  extremity,  </. 
a  win*/  or  /(turn,  d  e,  is  made  to  cover  the  part,  o  </,  from  the 
flank  and  reverse  fire  of  the  collateral  works;  this  part,  6?  d, 
may,  in  some  cases,  be  arranged  nearly  parallel  to  the  crot- 
chets, n  o,  of  the  covered-^iy,  so  as  to  give  a  fire  on  them; 
but  generally  it  serves  onlj-  to  cover  the  branch,  c  d,  as  has 
been  explained. 

18. ..There  are  two  ways  of  forming  the  cavalier,  depending 
on  the  nature  of  the  soil.  When  the  excavated  earth  is  pi 
such  a  nature  that  it  can  be  easily  made  to  stand  at  any  slope, 
a  pi-olile,  represented  by  Fig.  21 ,  is  preferred,  as  requiring  less 
time  and  materials.  After  having  laid  out  the  position  of  the 
cavalier  by  the  full  sap,  the  sappers  wixlen  the  trench  il',  and 
make  a  step  at  the  bottom  of  the  trench  22"  in  height,  and 
5'  0"  within  the  gabion  of  the  parapet;  this  step  serves  as  a 
platform  on  which  the  sappers  mount  to  level  the  earth  of  the 
parapet  even  with  the  fascines  on  top  of  the  first  gabion,  for 
the  purpose  of  placing  a  second  tier  of  gabions,  which  is  placed 


ATTACK   AND   DEFENCE   OF    PERMANENT    W0BKS.  305 

22"  beyond  tlio  first.  This  second  ten-  IS  filled  with  earth,  and 
crowned  with  two  fascines,  and  the  mound  is  raised  to  a  level 
with  the  fascines,  by  widening  the  trench  to  the  rear.    The 

earth  is  now  levelled  even  with  the  top  of  the  faaCUieB,  and  a 
third  tier  of  gabions  is  placed  just,  on  the  outside  of  the  second  ; 
it  is  filled  with  earth,  crowned  with  three  fcsoinea,  and  the 
mound  is  raised  to  a  level  with  the  upper  fascine.  Thif  t-.p 
tier  forms  the  parapet  of  the  work.  Loop-holes  are  made  1 » v 
arranging  sand-bags  on  top  of  the  parapet,  for  the  purpose  of 
covering  the  heads  of  the  aieii  whilst  in  the  act  of  firing.  As 
the  successive  tier.-  of  gabions  are  placed,  Steps,  revetted  with 
fascines,  are  made  to  lead  to  the  top;  these  steps  have  a 
%nd  tread  of  22" J  the  top  one  u  a  banquette.     f 

It). ..When  the  soil  eXCftV&ted  i.  loose,  a  cavalier  made  in  the 
manner  jttst  described  would  ool  be  sufficiently  firm.  Hie  fol- 
lowing construction  will  in  this  case  be  used  ;  After  having 
traced  out  the  cavalier  by  the  full  sap,  a  row  of  gabii 
22,  is  placed  in  the  bottom  of  the  trench,  along  the  foot  of  the 
interior  slope;  this  row  is  tilled  With  earth,  and  crowned  with 
two  :  .  and  earth  is  filled   in  between  it  and  the    interior 

slope,  and  brought  to  a  level  with'the  berm.  A  third  tier  of 
gabions  U  placed  on  this  platform,  alongside  of  the  row  form- 
ing the  parapet  of  the  trench;  this  tier  is,  in  like  manner, 

filled  with  earth,  and  crowned  with  two  fa 

tier  of  the  cava)  >oamenoed,  by  placing  a  fourth  row  .,f 

gabions  over  the  joint  of  the  two  in  the  fj 

with  earth,  crowned  with  two  B,  and  the  mound 

on  the  exterior  tp  a  level  witty  this  fourth  gabion.     >\  fifth 

\t  placed  al<  of  the  two  in  the  first  tier,  filled  with 

earth  and  crowned  with  I  -ii  is  then  pis 

aloi  the  fourth,  in  the  second  tier,  and    arranged   like 

the  preceding,     i  inally,  tie1  parapet  is  formed  on  this  t& 
tier,  by  placing  a  gabion  above  the  joint  bet* 

nd    tier,    and    ai  1 7.      'I 

made  to  Second  to  the  1"]',  by  tin  .irth, 

30 


306  A1TA<  K    ASD    Mil  N<  E   OF   PERMANENT    W0KK8. 

on  the  interior,  against  the  gabionade,  and  forming  the  surface 
into  steps  revetted  with  fascines,  as  in  the  last  case. 

DESCENTS  OF  THE  COVEEED-TVAY  AND  DITCHES. 

20...I'>i.im»i  i>  1>is(  knt.  "When  a  trench  has  to  he  pushed 
forward  in  a  position  where  the  command  of  the  dangerous 
point  is  so  great  that  it  cannot  be  sheltered  from  the  plunging 
fire  by  traverses,  it  is  covered  on  tli'c  top  and  on  the  Bidea  by 
fascines  and  earth  supported  by  a  framework,  and  is  termed  a 
hi 'i  ullage. 

But  this  method  of  obtaining  cover  is  principally  requisite 
in  trenches  which  descend  toward  the  dangerous  point ;  like* 
the  passages  which  lead  from  the  trenches  on  the  glacis  into 
the  covered-way,  and  to  the  hottoms  of  shallow  ditches.  The 
manner  of  forming  the  blindage,  Figs.  2o,  24,  is  to  set  up  a 
row  of  blindage  frames  along  each  side  of  the  trench  or  pus- 
sage;  to  connect  the  two  rows  at  top  by  like  frames  laid  across 
the  line  of  the  trench;  to  cover  the  top  frames  by  fascines  and 
earth;  and  to  fill  in  between  the  side  frames  and  the  sides  of 
the  trench  with  fascines.  The  trench  is  made  by  the  double 
sap.  Its  width  at  bottom  is  7'  6".  The  width  between  the 
frames,  6'.  The  frames  and  fascines  of  the  blindage  are  grad- 
ually placed  as  the  trench  advances,  the  latter  preceding  the 
former  about  5'.  The  work  is  begun  by  placing  an  upright 
frame  on  each  side;  the  two  are  next  connected  by  a  frame  on 
top,  one  side  of  which  is  lodged  on  the  top  cross  pieces  of  the 
upright  frames,  and  the  other  supported  by  two  auxiliary 
frames  until  the  next  two  upright  frames  are  placed;  the  fas- 
cines are  then  thrown  over  the  top  frame  to  the  depth  of 
about  2',  and  these  are  covered  with  earth  or  raw  hides,  to 
prevent  their  being  set  on  lire.  Fascines  are  at  the  same  time 
placed  in  on  the  sides. 

The  slope  given  to  the  bottom  of  a  blinded  descent  should 
not  be  greater  than  \.  "When  the  descent  is  to  a  covered-way, 
Figs.  23,  24,  the  bottom  of  it  should  debouch  into  the  covered- 


ATTACK    AND    DEFKNVK    OF    I'KKMA  \  1  NT    WORKS.  307 

way  at  -1."."  below  its  terrepleia  ;  this  will  serve  to  determine 
the  point  of  departure,  the  Blope  being  iivd.  which  Bhould  be 
;>'  below  tlie  surface  of  ilie  glacisj  ^o  that  when  the  blindage 
is  put  np  at  this  point  the  top  of  it  shall  not  be  above  the  level 
of  the,  parapet  of  the  trench.  A  horizontal  landing  about  8' 
in  breadth,  is  made  at  the  en  trailer  of  the  blindage;  add  this  is 
connected  with  the  bottom  of  the  trench  by  two  rani])-  of  1-<I. 

The  point  selected  for  B  Minded  de.-celit  into  a  coVeivd-way 
is  usually  at  the  end  of  a  traverse:  as  the  traverse  will  oover 
the  outlet  of  the  blindage  from  a  plunging  fire  in  front. 

21. ..A  descent  to  a  ditch  is  usually  hy   blindage,  when   the 
depth  of  the  ditch   does  not  exceed    l'T  or  12'.      For 
depths  the  commencement  <>f  the  descent  is  by  a  blind 
Fig.  25,  which  is  continued  to  a  point  where  the  bottom  of  the 
descent  is  about  U'  below  the  surface  of  the  ground;  here  the 
blindage  is  terminated,   and    the  remainder  of  the   descent  is 
made  by  gallery,  as  the  depth  of  the  earth  above  the  gal 
will  be  sufficient  to  allow  the  excavation  to  be  carried  on  with- 
out trouble.     In  a  firm  soil,  grand  gallery  frames  are  used  for 
the  descent ;  in  a  loose  soil,  common  gallery  frames.     The  con- 
struction of  the  gallery  is  the  same  as  for  a  mine  gallery. 

The  point  of  departure  of  a  ditch  descent  is  usually  I 
at  only  about  2'  below  the  bottom  of  the  trench;  the  usual 
landing  being  made  at  this  point.  In  a  (\ry  ditch,  the  bottom 
of  the  descent  debouches  at  the  usual  depth  of  the  tail  sap 
below  the  bottom  of  tin-  ditch.  In  a  wet  ditch,  it  should  come 
out  about  1.7'  above  the  water  level. 

I'  IBS  \<,I  -    OF    MT<  111  9, 

•_'_'.. .  I  >i:  v  Ditch.     The:  if  a  dry  ditch  is  nothi 

than  a  full  sap.  which    leads  from  the  on;  t  in 

the   ditch    to   the   bottom   of   '  I    h.      From  this  l 

trench  and  parapet  are  din  ct<  d  np»  the  brei 
wall,  which  foro 
«.n-  point.     The  onl\ 


308  ATTACK    AND    DEFKN.'i:    Of    PERMANENT    WoKKS. 

sage  is,  to  sink  the  trench  at  the  outset  to  its  full  depth  of  4:5" 
to  gs&n  secure  cover- 

23...AV  i  i  DncH.  The  passage  of  a  wet  ditch  is  a  perilous 
and  difficult  operation  trader  any  circumstances,  but  particu- 
larly so  when  a  strong  current  can  be  produced,  by  the  be* 
d,  in  the  ditch.  The  methods  usually  recommended  arc 
to  form  a  dike,  or  bridge  of  fascines  and  hurdles,  laid  in  suc- 
cessive layers,  and  firmly  connected  by  pickets.  To  form  a 
footing  tor  the  dike,  a  grand  gallery  is  excavated,  directly  be- 
hind the  counterscarp  wall,  to  a  distance  of  12'  or  15'  on  each 
side  of  the  descent,  and  the  earth  from  it  is  thrown  into  the 
ditch,  through  the  outlet  of  the  descent.  The  dike,  or  bridge 
of  fascines  is  gradually  pushed  forward  from  this  point,  being 
secured  in  the  best  way  practicable  to  the  earth  thrown  into 
the  ditch.  The  sappers  who  carry  forward  the  head  of  the 
dike  are  covered  from  the  fire  of  the  dangerous  point  by  a 
musket-proof  mask  of  fascines  and  boards,  attached  to  a  raft 
on  which  they  work.  The  (like  should  be  from  12'  to  15'  wide 
at  top.  A  gabionade  parapet  is  placed  on  it  toward  the  dan- 
gerous side.  It  is  formed  of  two  tiers  of  gabions,  tilled  with 
earth.  The  bottom  one  consists  of  two  rows  of  gabions,  each 
crowned  with  two  fascines — the  two  rows  being  in  juxtaposi- 
tion ;  the  top  tier  is  a  single  row  crowned  with  three  fascines. 
The  top  of  the  dike  is  covered  by  a  layer  of  earth,  and  the 
parapet  with  raw  hides,  to  prevent  the  effects  of  incendiary 
compositions  that  might  be  thrown  on  them.  Raft-bridges, 
on  barrels,  protected  by  a  gabionade  parapet,  have  also  been 
proposed,  particularly  where  a  strong  current  is  to  be  contend- 
ed with. 

BATTERIES. 

24... Enfilading  and  Counter-batteries.  These  batteries 
are  used  for  destroying  the  artillery  and  silencing  the  fire  of 
the  defences.  Positions'  are  chosen  for  the  first  from  which 
the  terrepleins  of  the  faces,  that  bear  upon  the  ground  on 
which   the  parallels  and  approaches,  are  laid  out,  can  be  en- 


ATTACK   AND    DEI  1  \<  I     OF    PERMANENT    WORK8.  809 

filaded  ;  the  second  are  so  placed  that  they  «:ui  bring  a  direct 
or  a  slant  fire  against  the  embrasures  of  the  points  to  be 
silenced.  The  shot  from  the  former  la  thrown  with  small 
charges,  under  angles  of  elevation  <>f  from  0°  to  1>°,  so  as  to 
ricochet  along  the  terrepleins,  taking  the  guns  of  tin*  defences 
in  flank;  the  latter  fire  with  full  charges  directly  against  the 
j.oinl  to  be  attained. 

25...  As  the  effects  of  both  direct  and  enfilading  lire  vary 
greatly  with  the  range,  positions  should  be  chosen  for  these 
batteries  as  near  the  defences  as  they  can  he  tlimwn  np  with- 
out too  great  a  sacrifice  of  life.  Positions  which  will  give 
ranges  between  3(J0  yards  and  7"<»  yards,  are  the  best  i  nearer 

than  300  yards,  the  workmen  would  be  exposed  both  to  the 

Are  of  musketry  and  case  shot:  beyond  7"*"  yards,  the  lire 
upon  the  defences  becomes  very  uncertain.  The  besl  points 
for  these  batteries  are,  therefore,  on  the  tone  of  ground  occu> 
pied  by  the  first  and  second  parallels;  the  former  being  at 
about  i'xmi  yards,  and  the  latter  about  8Q0  yards,  from  the 
most  salient  points  of  the  defene. 

96.. .The  batteries  may  be  placed  either  within  the  parallel, 
in  advance  of,  or  in  rear  of  it.      The  positions   usually  selected 

are  from  20  yards  to  80yards  in  front  of  the  parallel;  because^ 

if  placed  within    it.  there    might    be    mutual    interference    be- 
tween the  service  of  the  batteries  and  that  of  the  parallel :  i 
unhss  placed  soi listauce  iii  the  rear  of  it.  the  parapet  of 

the   parallel   might   obstruct    the   shot    of  the    battery,  and  the 

troops  in  the  tr<  neb  be  annoyed  by  the  fire. 
The  most  effective  positions  for  these  bati  i 

of  the  second  parallel;  and  unless  ti 

very  destructive,  it  will    l.e  beat   to   plaoc   them   th<  re.     If 

placed  in  front  of  the  first  parallel,  it  will  be  necessary 

the    most    Of    them    to    the  liv-nt     of    '  'd    "parallel    » 

after  the  latter  is  thrown  up.      For  the   third    parallel. 
Hppr  ading  to  it  from  the  second  parallel,  run  I 

of  being  attained  by  shot  from  ba 
in  their  i  be  first  parallel. 


310  ATTAriv    AMD    m.lT.XCK    OF    rEItMAM  XT    WolJK-. 

27. ..The  site  of  the  platforms  of  the  batteries  may  cither  he 
on  the  surface  of  the  natural  ground  or  sunk  below  it.  In  the 
latter  case,  the  battery  is  termed  a  sunken  battery.  In  the 
former  case,  the  parapet  of  the  battery  is  obtained  from  a 

ditch  in  advance  of  it  ;  in  the  latter,  it  is  got  from  a  trench  in 
it>  rear.  In  the  sunken  battery,  the  labor  of  construction  is 
lees,  and  the  men  engaged  in  making  it  are  placed  more 
dily  under  cover  than  in  tic  other  kind.  Sunken  batteries 
can  only  he  ttsedj  however,  when  the  trenches,  or  other  ele- 
vated points,  in  advance  of  the  batteries,  which  lie  in  their 
field  of  tire,  will  not  intercept  the  shot;  and,  as  a  general  rule, 
these  batteries  should  be  placed  only  in  positions  where  their 
field  of  fire  is  completely  unobstructed  by  the  trenches. 

28.. .The  interior  crest  of  an  enfilading  battery  should  be 
nearly  perpendicular  fce  the  prolongation  of  the  line  to  be  en- 
filaded; and  be  so  placed  that  the  shot  from  all  the  guns 
shall  sweep  the  terreplein  throughout  its  entire  length;  The 
position  of  a  battery  that  will  satisfy  this  last  condition  can  he 
readily  found,  as  it  must  evidently  lie  within  the  angle,  formed 
by  producing  to  the  exterior  the  diagonals  of  the  terreplein  to 
be  swept.  The  best  position  of  the  guns  will  be  to  place  one 
so  that  its  line  of  fire  shall  be  nearly  on  the  prolongation  of 
the  interior  crest  of  the  line  enfiladed,  and  the  remainder  on 
that  side  of  this  one  on  which  the  exterior  line  of  the  terreplein 
prolonged  may  fall. 

29. ..In  a  counter-battery,  the  interior  crest  should  be  nearly 
parallel  to  the  line  to  be  counter-battered.  A  position  some- 
what oblique  to  the  line,  so  that  the  shot  of  the  battery  may 
enter  the  embrasures  obliquely,  is  also  a  good  one  for  tearing 
away  the  cheeks  of  the  embrasures,  and  exposing  the  guns  of 
the  defences. 

30. ..Whenever  a  position  has  to  be  taken  up  for  an  enfilad- 
ing or  a  counter-batterv,  in  which  the  .direction  that  can  be 
given  to  the  interior  crest  is  very  oblique  to  that  which  it 
ought  to  receive,  it  will  be  necessary  to  make  the  embrasures 
of  the  battery  with  a  corresponding  obliquity  to  the  direction 


ATTACK   AND   DEFENCE   OP    PEBKANEHT   WORKS.  311 

of  the  parapet;  and,  to  avoid  the  inconvenience  of  these  last, 
it  -will  be  farther  necessary  to  break  the  interior  crest  Into  an 
indented  line,  to  allow  the  muzzles  of  the  gam  to  be  run  the 
Requisite  distance  into  the  embrasures;  placing  one  side  of  the 
indent  perpendicular  to  the  axis  of  the  embrasure,  and  the 
other  parallel  to  it. 

&k. ..Enfilading  and  counter-batteries  are  usually  armed  with 
18  and  24-pounders,  and  8-inob  howitzers.  The  fire  of  the 
gttns  is  mainly  directed  to  destroy  the  artillery  of  the  di 
that  of  the  howitaera  to  sweep  the  eovered-ways  and  ditches, 
to  destroy  the  palisadings,  and  injure  the  traverses  by  the  ex- 
plosions of  the  shells  that  may  lodge  in  them.  A-  a  general 
rule,  there  need  not  be  more  than  seven  piece-,,  nor  should 
there  usually  be  less  than  three  in  anyone  battery;  the  num- 
ber depending  upon  the  bearing  which  the  artillery  of  the 
part  to  be  silenced  may  have  upon  the  ground  on  which  the 
works  of  the  besiegers'  must  be  placed.  Tin-  batteries  should 
he  as  far  asunder  as  practicable,  so  as  not  to  invite  a  coi 
tration  of  the  tire  of  the  defences  upon  any  point  by  the  accu- 
mulation of  a  large  number  of  pieces  on  it,  and  thus  multiply 
the  chances  of  loss  both  to  the  treops  and  ?//'//< 

32. ..In  computing  tin-  extent  of  front  of  a  Lattery,  PI.  11, 

Fig.  •-'''>.  an  allowance  of    1"'.  1  alotlgthe  LI 

is  made  tor  each  piece,  and  <">'  for  each  splinter-proof  gabionade 

traveive,  one  of  which  is  placed  between  every  two  gun s,  when 

there  are  more  than  three  in   a  battery.     The  flanks 

guns  are  covered  by  an  epaulment  thrown  up  .  or  both 

extremities  of  the   parapet.     The  length  of  the  epauln 

measured  along  its  interior  crest,  may  he  from 

direction  of  the  epaulun  m  with  respect  to  the  parapet  will 

depend  on  that  of  the  lire  of  t'i.   ,  ;il    rule, 

the  interior  <t<  91  of  the  epaulment  shonl  I 

about  100°  with  that  of  the  parapet.     Wh 

on  the  natural  surface,  the  earth  fof  the  parapet.  <  paulm 

and  tra\  1  1  ditch  in  fro:  | 

epaulm<  tits,  and    1  ara  A 


312      ATTACK  AND  DEFENCE  OF  PERMANENT  WO  I. 

narrow  ramp,  at  the  end  of  eacli  epsulment,  leads  from  the 
natural  level  to  the  bottom  of  the  ditch,  and  serves  for  the 
convenience  of  the  men  whilst  throwing  up  the  battery.  A 
trench,  of  the  ordinary  dimensions  of  an  approach,  and  defiled 
from  dangerous  points,  leads  from  each  extremity  of  the  bat- 
tery co  the  parallel  in  its  rear. 

33. ..If  the  embrasures  are  so  oblique  as  to  require  an  in- 
dented parapet,  the  side  or  face  of  the  indent,  through  which 
the  embrasure  is  pierced,  should  be  2:>',  and  perpendicular  to 
the  axis  of  the  embrasure.  The  other  side,  <>r  flemk  of  the 
indent,  should  be  25',  and  parallel  to  the  axis;  a  distance  of 
only  7'  being  left  between  these  two  last  lines,  to  give  all  the 
thickness  practicable  to  the  portion  of  the  merlon  that  forms 
the  outer  angle  of  the  indent ;  for  a  like  reason  the  face  of  the 
indent,  at  the  extremity  of  the  battery,  should  extend  21'  be- 
yond the  axis  of  the  embrasure.  These  data  will  serve  to  esti- 
mate the  tofcil  length  of  the  parapet.  Its  thickness,  estimated 
from  the  inner  angles  of  the  indents,  is  18'. 

34.. .The  profile  of  a  battery  will  depend,  both  for  its  dimen- 
sions and  form,  on  the  command  of  the  point  from  which  it 
can  be  attained,  and  on  the  position  of  the  surface  of  the 
ground,  on  which  it  is  laid  out,  with  respect  to  the  defene- 

Where  the  site  of  the  Battery  is  horizontal,  and  the  com- 
mand of  the  defences  over  it  is  within  the  usual  limits  of  20' 
to  30',  the  following  forms  and  dimensions,  Fig.  27,  will  afford 
ample  cover  to  the  men  and  materiel  of  the  battery,  when  the 
platforms  are  on  a  level  with  the  natural  surface  :  Height  of 
the  interior  crest,  T  6".  Thickness  of  parapet,  18'.  Interior 
slope,  4-1.  Superior  slope,  1-12.  Exterior  slope,  the  natural 
slope  of  the  earth.  The  same  dimensions  and  forms  may  be 
given  to  the  epaulments,  except  the  distance  between  their 
interior  and  exterior  crests,  which  may  be  reduced  to  12'  when 
the  direction  of  the  epanl incut  is  quite  oblique  to  that  of  the 
fire  of  the  defences.  h\  the  contrary  case,  this  distance  should 
be  18'.     The  depth  of  the  ditch  is  taken  at  5';  its  width  will 


ATTACK    ANT)    DEFENCE   OF   PERMANENT    WORKS.  813 

be  regulated  by  the  quantity  of  earth  to  be  furnished  for  com- 
pleting all  the  parts  of  the  battery. 

35. ..The  axes  of  the  embrasures)  Pigi  26,  are  Is'  apart,  ex- 
cept at  tlic  points  where  splinter-proof  tra/verses  are  placed — 
the  requisite  distance  at  these  points  being  24',  allowing  0'  for 
the  width  of  the  base  of  the  traverse.  The  sill  of  the  embra* 
sure  is  3'  6"  above  the  platform  for  guns  mounted  <>u  tin-,  ordin- 
ary siege  carriage.;  its  sole  is  parallel  to  the  superior  slope. 
The  mouth  of  the  embrasure  is  of  a  trapezoidal  form,  being 
2'  wide  at  bottom  and  •">'  at  top.  The  splay  of  the  sole  is  ob- 
tained by  giving  the  sides  an  inclination  of  1-1"  with  the  axis. 
The  top  line  of  the  cheek  is  obtained  by  setting  off  along  the 
direction  of  the  exterior  crest,  from  the  point  where  the  side  of 
the  sole  cuts  it  in  projection,  one-half  the  vertical  distance  be- 
tween these  two  last  lines,  and  joining  the  point  thus  found 
With  the  exterior  point  of  the  mouth  at  top. 

Embrasures  of  howitzers  may  receive  a  counter-slope,  giv- 
ing the  sole  nearly  the  same,  inclination,  from  the  sill  upward, 
a>  the  feast  angle  of  elevation  under  which  it  may  be  required 
to  aim  the  pi< 

B6.,.The  parapet  of  the  battery  and  the  embrasures  arc  re- 
vetted either  with  gabioas,  fascines,  or  sand-bags,  or  with  a  coop- 
binatioD  of  th 

The  epaulmenta  need  not  be  revetted,  their  interior  si 
being  made  as  Bteep  a-  the   earth    will   stand    at.     Ihe   gabion 
revetement- is  the  firmest  and  most  durable.     Wlien   u-<  <}  far 
the  parapet,  two  tiers  will  be  requisite. 

The  requisite  slop<  •  o  to  the  gabions  of  the 

by  placing  a  row  of  under  them,  alo«  . 

interior  alopi  >ther  row  of  fi  s  laid  on  to] 

tier,  along   tic   interior  slope,  on   which  the  gabioi 

[uisite  height 
either  by  pla  Is  on  the  top  ti«i-  or  by  <  arth  alone.   W 

e  used  *  laid   in   - 

interior 

4U 


314  ATTAi  k    A.vn    DEFEftOB   0*    im  i:m\nv\t   WoKKS. 

imr  joint.  To  give  the  bags  greater  durability,  they  should  l>o 
impregnated  with  tar  before  being  filled. 

It  has  been  found  that  raw  hides  will  preserve  the  rev< 
ments  of  tin-  cheeks  from  the  effects  of  die  concussion  pro* 
duqed  by  the  firing,  ror  this  purpose,  the  bide  is  folded  with 
the  hair  inward.  It  is  confined  to  the  top  of  the  cheek  by 
pickets  driven  through  it  into  the  merlon;  and  at  the  month, 
arid  the  other  end  of  the  check,  by  packets  driven  into  the  re- 
vctement.     The  lower  end  is  allowed  to  hang  loose. 

87.. .The  splinter-^roof  traverses'^  Fig.  2&,  arc  formed  of  two 
tiers  of  gabions.  He  lower  tier  consists  of  two  parallel  rows  of 
eabions,  and  is  .v  wide  at  the  base;  the  rows  of  gabions  are 
slightly  inclined  toward  each  other  at  top.  The  upper  tier 
also  consists  of  two  rows,  which  rest  on  two  roWB  of  fascines, 
laid  on  the  first  tier,  the  gahions  leaning  against  each  other  at 
top.  The  gabions  and  the  space  between  them  are  well  tilled 
in  with  earth,  which  is  heaped  above  the  top  tier.  The  tra- 
v.t.-c  may  he  from  15'  to  IS'  long.  A  passage-war  of  2'  is  left 
hetween  the  parapet  of  the  battery  and  the  end  of  the  traverse. 

38. ..Thi'  platforms  are  Itf  6"  wide.  15'  long  in  the  (dear,  and 
receive  an  upward  slope  ot  7"  to  s"  from  thehurter  to  the  tail. 
They  are  composed  of  6  keepers,  each  l.V  long  and  5"  on  the 
,idr  :  of  L2  ].lanks,  each  lo'fi"  long  and  2" thick;  of  2  ribands, 
or  side-rails^  of  the  dimensions  of  the  sleepers;  and  of  a  lmr- 
ter.  The  sleepers  are  firmly  imbedded  in  the  ground,  and  se- 
cured by  stout  pickets  at  their  ends.  The  planks  are  (damped 
between  the  side-rails  and  outside  sleepers,  these  pieces    being 

connected  firmly  either  by  screw-bolts  and  nuts  or  by  rack- 
lashings. 

39... In  sunken  batteries,  the  same  length  of  interior  crest  is 
allowed  for  each  guh  as  in  the  preceding  case;  but  when  the 
battery  requires  splinter-proof  traverses,  an  allowance  of  86'  is 
made  for  the  distance  between  the  axes  of  the  guns  separated 
bv  a  travel-si'.  The  position  and  length  of  the  epanhnents  arc 
also  determined  as  in  the  preceding  case. 

40. ..The  trench  of  the  battery,  Fig.  29,  when  first  excavated 


ATTACK    AND    DEFENCE   OH    PERMANENT    WoUKS.  315 

• 

is  ir>'4R-iilo  at  bottom,  3'  deep  in  front,  and  2'  6"  deep  in  reard 
The  front  Is  cut  down  vertically  in  firm  soil,  and  the  revi 
receives  a  Blope  of  A.    [Die  interior  crest   of  the  parapi 
4'  6"  above  tie  natural  surface;  the  parapet*  1 8'  thick)  the 
interior  slope,  4-1  ;  the  exterior  Blope,  1-1.     A  berm  of  t$"  is 
lot't  between  the  parapet  and  the  trench  when  first  excavated. 

•11. ..As  the  dimensions  above  given  to  the  trench  will  fur- 
nish earth  only  for  the  parapet,  that  required  for  the  epanl- 
ment  is  taken  from  a  ditch  5!  deep  exterior  to  it:  and  a  small 
portion  of  ditch  is  made  exterior  to<  the  parapet,  and  opposite 
the  position  of  each  splinter-prqpf  traverse,  to  provide  the 
earth  requisite  for  the  traverse,  and  which  is  taken  from  tin' 
trench..  The  epaulment,  if  exposed  only  bo  an  oblique  tire, 
need  not  be  thicker  than  L2'. 

4:2. ..The  embrasures  receive  the  same  form,  dimensions,  etc., 
as  in  the  precedii  § 

■t-'!...The  front  of  the  trench   is  revetted  with  fascines.    Xo 
put  up  this  revetement,  the  trench  is  widened  by  cutting  av 
the  front,  nearly  to  the  width  of  the  benn,  and  almost  verti- 
cally.    Thi.>  will  admit  the  muzzles  of  the  iznu>  to  he  run  well 
into  the  embrasures. 

T.i  avoid  the  labor  and  exp  .  it  has  hcen 

proposed  neither  to  revet  the  portidn  o/  the  trench   bord< 
the  epanlment,  not  the  interior  slope  of  the  epaulment;  hut  to 
■  at  this  part,  •"''  wide,  when  the  trench 

instruction,  and.  afterward,  to  Lrive   both  to  this  portion  of 
the  trench  and  the  interior  of  the    epaulmeni 
as  the  earth  will  stand  well  under. 

44... When  splinter-proof  tra\  <  r»  -  are  i  i  of 

the  ground,  <'»'  wide  on  which  the  travert 
The  traverse  is  made  by  first  placing  two  parallel  ron 
cines  at  .V  apart,  on  which  a  tier  of  gabioi 

touch  a' 
is  tilled  in  the  gabions  and  tl 
keajfi  d  up  i 

Tin 


316  ATTAi   K     AM'    MM. N.I      09    ITKMAMM     WoKK>. 

able  slope,  and  revetted  with  fascines.     A  passage  of  _'■%  left 

between  the  gabionade  of  tin-  traverse  and  the  interior  slope 
of  the  parapet. 

45. ..To  provide  against  rainy  weather,  two  of  more  holes 
should  be  dog  at  Buch  point*  of  the  trench  of  the  battery  m 
may  be  found  most  convenient  to  receive  the  water  that  col- 
lects in  tin-  trench;  and  precautions  should  be  taken  to  pre- 
vent  water  from  being  received  into  the  trench,  either  through 
the  trenches  leading  to  it  or  from  the  natural  surfac. 

4<'>...Tlie  powder  magazines  shctuld  be  at  least  3o'  in  rear  of 
the  parapet  <>f  the  batter.^.  The  ceiling  of  the  magazine 
should  not  he  more  than  a  few  inches  above  the  natural  level. 
The  interior  height  need  not  be  more  than  .V.  The  width  may 
be  G',  and  the  length  12',  in  the  clear.  The  sides  ot  the  maga- 
zine may  he  formed  of  frames  ami  sheeting  boards;  or  of  a 
row  of  gabions  crowned  with  two  courses  of  fascines.  The 
magazine  is  covered  at  top  by  splinter-proof  timbers,  f."xl'", 
laid  in  juxtaposition,  and  covered  with  at  least  3'  of  earth, 
both  on  top  and  on  the  .-.ides  toward  the  parapet.  A  passage 
lend-  into  the  magazine,  on  the  aide  from  the  parapet,  which  is 
reached  by  one  or  two  inclined  trenches. 

4VT..vMoETAB  Haiti  kiks.  There  are  two  kinds  of  mortar 
batteries  used  in  the  attack:  those  lor  mortars  throwing  >hells, 
and  those  for  mortars  throwing  baskets  of  stones,  or  other  like 
projectiles.  Besides  these, there  is  theCoehorn  mortar, which, 
from  its  small  size,  mav  he  placed  in  any  nnobcupied  corner 
of  the  trenches.  The  first  kind  of  batteries  may  hi'  in  front  of 
the  first  and  second  parallels,  or  on  any  other  points  farther 
back.    The  positions  ehoeen.fbr  them  should  he  mch  as  to 

bring  as  greal  a  portion  of  the  defences  under  the  direction  of 
their  lire  as  practicable,  to   increase   the    chancer  of  destructi- 

bility  of  each  shell  thrown.  The  secood  kind  are  placed  in 
front  of  the  third  parallel,  mainly  with  a  view  to  annoy  the 
covered-ways  and  parts  adjacent. 

4S...The  platforms  of  these  batteries  may  be  laid  on  the*  nat- 
ural   surface,   in   which    case,   the   same  forms  and  dimensions 


ATTACK    ami    DEFENCE   09    I'IKMWim    W6JRKS.  81T 

will  bo  given  to  the  parapel  and  epaulmento  of  the  battery 
in  gun  batteries;  but  as  the  mortars  must  be  set  back  from  the 
parapet,  to  enable  the  shell  to  clear  the  interior  crest  by  about 

3',    a    lWeteinelit    will    Hot    lie    nece.->;^-y.  and  tlie  |  .:ir:i|  >et   may 

ei  oeive  as  great  an  interior  slope  at  the  earth  can  be  made  to 
stand  under  firmly. 

■1!'.. .The  front  of  a  mortar  battery  is  estimated  by  allowing 
15'  for  eaeli  mortar,  and  <;'  for  each  splinter-proof  traverse. 

Those  batteries  are,  however,  usually  sunk'  below  the  natu- 
ral surf,  several  feet  difference  of  level  in  the  position* 

of  a  mortar  will  have  hut  little  etlect  on  the  range  or  the  tra- 
jectory. The  profile  suitable  tor  such  positions,  under  ordinary 
eircumsl  -  the  following:  Width  of  treach  at  bottom, 

13'  »i".  Depth  in  front  8'  «i".  Depth  in  rear.  f.  Reserve 
slope,  h.  Front  slope.  W  bate.  If  ight  of  parapet,  41.  Thick- 
m  m  of  parapet^  l v'.     Berm,  1'. 

60... The  earth  tor  tlie  epaulment  is  taken  from  ai 
ditch  ;  and.  when  splinter-proof  traversi  -  are  required,  por- 
tions  of  ditches  are  made  oppoBiu  \->  their  position,  to  furnish 
the  requisite  earth. 

51...The  platforms  of  mortars  are  T  6"  long  by  &  6"  wide. 
jThoy  are   composed   of  two   ground-sills,   T  '">"  long   and    *;" 
squ  ion-  and  »''"  sqoai 

long  and  4"  square;  8  planks,  each  6' <T  long  and  4'*  thick. 
The  ground-siUs  are  laid  horizontally,  and  firmly  embedded  in 
the  ground  at   4'  6"  apart,  and   transversely  to  the  - 

1  ]>on   these  the   -  confined  by  I 

i  ml.     The  plank  I  the 

pen  mi  1  gun  plat 

■  'J...  I  '.i.  i     '  ■  I  .\poM   d        ]  .  -        1,0 

breached  by  heavy  gui 

and   batter*  B  thrown   up  iii  sud 

tho- 

the  breach   1 

I 


318  ATTACK    AND    1  >!■:!■  l  M  K    09    I'lKMAMM     \\oi;k>. 

fences,  at  points  where  no  obstruction  will  intervene  to  p 
vent  the  fire  of  the  guns  from  being  directed  at  a  point  of  the 
wall  to  be  opened  low  enough  to  form  a  breach  practicable  to 
the  ascent  of  an  assaulting  column 

In  either  of  the  tatter  cases  the  batteries  must  he  sunk:  the 
level  chosen  for  the  platforms  being  such  as  to  subserve  the 
object  in  view.  The  embrasures  in  these  cases  are  usually  cut 
out  of  the  parapet,  as  an  ordinary,  trench  has  generally  to  he 
first  established  as  a  preparatory  step  to  commencing  the  bat- 
tery* The  forms  and  dimensions  adopted  for  other  sunken 
batteries  will  apply  to  these  cases,  with  such  modifications  as 
may  be  demanded  by,  the  site  of  the  battery,  and  the  position 
of  the  point  to  he  attained  by  the  fire. 

When  a  hreach  battery  Is  established  either  on  the  glacis 
or  upon  the  terrcplein  of  a  work,  its  guns  will  generally  he 
exposed,  both  on  their  flank  and  rear,  to  the  lire  of  dangerous 
commanding  points,  from  which  it  will  he  necessary  to  cover 
them  by  traverses.  The  number  of  traverses  and  their  posi- 
tion will  depend  upon  the  command  and  position  of  the  dan- 
gerous points.  To  cover  from  the  flank  fire,  if  the  command 
of  the  dangerous  point  is  considerable,  like  that  of  a  cavalier 
retrenchment,  it  may  be  necessary  to  place  a  traverse  betweed 
every  two  nuns,  or  even  between  each.  The  traverses  used  in 
such  cases  receive  a  thickness  of  14',  or  seven  gabions,  like 
those  for  covering  an  ordinary  trench  from  as  entilading  lire  ; 
their  length  will  depend  upon  the  relative  positions  of  the 
dangerous  point,  and  the  exterior  point  of  the  battery  to  be 
covered  ;  their  height  is  usually  not  greater  than  the  traverses 
for  a  trench.  m 

When  the  reverse  of  the  battery  is  exposed,  it  will  generally 
arise  from  the  salient  position  of  some  comparatively  distant 
point,  from  which  a  slant  fire*  may  he  brought  to  hear  on  this 
part  of  the  battery  ;  in  which  case  it  will  generally  he  easy  to 
cover  the  part  exposed  by  running  out,  from  the  reverse  of  the 
battery,  an  end  of  trench,  to  form  a  wing  traverse  that  shall 
intersect  the  lines  of  fire  of  the  point  upon  every  part  exposed. 


ATTACK    A\P    DEFENCE    01    l'lKM.wiNT    WOBK0.  319 

54.. .The  nuns,  of  breach  batteries  should  bo  so  placed  that 
the  direction  of  their  fire  may  be  as  nearly  perpendicular  m 
practicable  to  the  line  of  wail  to  be  breached  ;  and  where 
these  lines  are  oblique  to  Bach  other,  the  obliquity  should  Dot 
exceed  4f>°,  otherwise  the  effect  of  the  shot  will  be  greatly  di- 
minished,-and  the  operation  retarded. 

Besides  the  breach  batteries,  it  will  »be  necessary  bo  place 
counter-batteriea  on  the  glacis.  Their  object  will  be  to  conn* 
tor-l>atter  and  silence  tlie  artillery  of  those  portions  of  tlio  de- 
fences which  can  be  brought  to  bear  on  the  broach4)atterie&, 
or  on  the  passages  of  the  ditehea.  These  batteries  will  netialty 
be  placed  on  the  prolongation  of  the  ditches  of  the  deferti 
Tlieir  arranireiin mt  will  be,  in  all  respects,  the  same  as  that  of 
the  breach  batti  ri 

SIEGE  <)Pi;k.\tk»\s. 

55...The  operations  of  a  siege  are  usually  divided  into  three 
epochs.  In  the  first  are  comprised  the  investment,  and  other 
operations,  preliminary  to  breaking  ground  against  the  work) 
or   opening  the  trenches.     T  od  comprises  the  labors 

from  the  opening  of  the  trenches  to  the  completion  of  the 
third  parallel.  The  third,  the  subsequent  operations  to  the  tar 
faction  of  tin'  work. 

Fmsi    P]  !•; 

i  mim.    This  ii  the  fir-t  acttve  operation  of  the 

1m  sieging  foi  >bject  being  to  cut  off  all  communicnl 

bet'-'  garrison  and  the 

y    kind    from    being  1  •    the   work.   ' 

ything  in  its  vicinity  that  might  in  any   1 
ble  to  th<  >U,  and.  finally,  t 

of  the  defence 

For  tii'  11I  attainmei  I 

force,    which    is   mainly,   if  1 
should  move  Upon   the    work    with    c< 


320  ATTACK    AND    DEFENCE   OF   PERMANENT    WoKK<. 

.iftor  surrounding  and  Btecaring  all  avenue-  to  it,  should  send 

(Hit  detachments  to  scour   the   environs  no  ti)  the  Very  gates  of 

the  work,  if  practicable.  an<l  bring  off  with  them,  or  destroy, 
all  persons,  cattle,  provisions,  etc.,  met  with.  A  chain  of  posts 
and  sentinels  is  in  the  meantime  established   in  the  best  | 

lions  to  prevent  all  ROCeSfl  to  the  work  or  egress  from  it;  cafe 
being  taken  to  seled  for  the  post  points  which  are  not  ex- 
posed bo  the  artillery  of  the  work,  or  are  beyond  its  range* 
The  posts  occupied  by  the  troops  during  the  day  time,  and 
termed  the  </iiihj  <-i>nh>n,  are  shitted  at  dark,  and  points  nearer 
the  work  are  taken  np.  to  form  the  nightly  <-<>r<I<m<  ami  hem  it 
in  more  closely.  The  posts  and  sentinels  for  this  purpose 
should  be  pushed  as  far  forward  as  they  can  find  shelters  from 
the  musketry  of  the  defences;  and  under  their  protection  the 
reconnoitcring  officers  should  spare  no  efforts  to  gain  an  exact 
idea  of  all  the  ground  exterior  to  the  work,  and  of  the  char- 
acter of  the  defences. 

57. ..Posting  Besieging  Force.  The  main  body  of  the  be- 
sieging army,  with  the  engineer  and  artillery  siege-trains  fol- 
lows closely  upon  the  investing  corps,  to  prevent  the  line  taken 
up  by  the  latter,  which,  from  its  extent,  is  necessarily  weak, 
from  being  forced  either  by  the  garrison  or  by  strong  detach- 
ments from  without.  The  positions  for  the  camps  of  the  various 
corps  are  designated  by  the  commanding  general,  after  a  care- 
ful reconnoissance.  These  are  placed  beyond  the  range  of  the 
heavy  artillery  of  the  work,  with  their  color  fronts  facing  from 
the  work,  and,  as  far  as  practicable,  on  points  favorable  to  the 
health  and  comfort  of  the  troops,  and  the  defence.  Whenever 
natural  obstacles  occur  between  tin:  camps,  they  must  be 
crossed  by  good  lines  of  communication,  so  that  no  impedi- 
ment may  be  offered  to  the  speedy  concentration  of  the  troops 
upon  any  point  threatened  from  without. 

Besides  the  positions  taken  up  for  the  camps,  the  besieging 
force  will  also  occupy  all  points  exterior  to  the  camps,  within 
cannon  range,  by  which  they  are  commanded,  securing  them 


ATTACK    AX1)    IlKFKM  I'    Of    l'i:i;MA\'\l     WOBKS,  321 

by  field-works  of  sufficient  strength   to  Bubserre  the  eud  in 
view. 

58. ..In  i  1:1  \«  iimknis  of  Damps*  'the  front  and  the  rear  of 
i camps  are  also  secured  by  lines  of  field-works.  The  exterior 
works,  termed  the  A///-  of  C&rcwnvallatum,  should  fornJ  an 
Unbroken  line  of  intrencliments,  composed  of  the  most  simple 
elementary  parts,  as  tenailles,  redans,  etc.,  with  a  slight  pro- 
file; its  ehtef  object  behig'to  prevent  sncc  nail  detach- 
ments from  slipping  into  the  place.  The  interior  line, 
the  /.''/'  of  Ckfunfamattatioto)  is  composed  of  detached  works. 
which,  if  the  garrison  is  strong,  should  be  in  defensive  relation's*. 
The  main  points  which  shottkj  be  occupied  o-y  the!  .  are 
the  principal  avenues  to  the  defences,  and  the  p 
for  the  parka  of  the  siege  train,  to  Becure  these  points  from  the 

attempts  of  the  garrison*  and  to  reA4er  the  entrai f  lai 

convoys  into  the  defences  impracticab 
These  lines  are  placed  about  200  yards  id  front  and  rear  of 

the  camps. 

59. .'.In  the  later  sieges  in  Europe,  lines  of  circumvallation 
particularly,  were  seldom  resorted  t«»:  the  btesi  ateriting 

themselves  TOth  occupying  only  the  main  points  of  their  ; 
tion  by  field-Works,  and  giving  tin-  intervening  space  such 

nld  be  afforded  bj  strong  patrols  and  posts.    This 
departure  Prom  former  practic  .  in  most  From  tho 

want  of  strength  of  the  besieging  force,  anii  ntly 

attended  by  the  vi-v  events  against  which  lines  are  chi 
effectual  in  guarding.     Aa  a  field  of  battf  < 
force  Of  sufficient  strength  to  cope  with  tfa  ing  artni 

tion  taken  behind  a  line  of  circuravallation  is,  but 
ligible — a  maxim  that  applies  t<.  all  i 
-\\-<':d;  ! in.  - :  and  in  almost  everj 
has  been  made  igai   -'     ich  ; 
and  has  i  heavy  his*  on  th< 

'-,  let  t! 
oj-e'ii  to  this  obj< 
able    f<«r    tip 
41 


322  ATTACK     AM'    DJUXNUJI    OT    11  KMANINl     WoKK-. 

they  ought  to  be  thrown  up  in  nil  cases  when'  the  moans  of 
tlie  best  will  admit  of  it. 

$0i..PBBPA&ATl!ON8  l"i:  OPEBOfTG  Till     TsSNCHXB.      "Whilst  the 

besieging  force  is  occupied  in  arranging  and  securing  their  , 
camps,  a  portion  of  it  is  employed  in  preparing  the  trench 
material.-,  establishing  the  parks,  and  getting  everything  in 
order  preparatory  to  breaking  ground  against  the  defence 
At  the  Bame  time,  close  reconnoissances  ami  careful  instru- 
mental surveys  are  made  by  i&e  staff  corps,  to  obtain  <hitii  for  a 
map  of  the  defences  and  their  environs,  with  a  view  of  draw- 
ing up  a  plan  of  attack.  "With  this  object,  the  bearing  and 
prolongations  of  the  fates  an4  capitals  of  all  the  defences 
should  he  carefully  laid  down;  the  character  of  the  defences 
on  every  assailable  point  noted  ;  that  of  the  parts  bearing  on 
these  points,  and  the  nature  of  the  ground  over  which  they 
must  be  approached. 

Gl...Thc  parks,  magazines  of  powder,  and  other  depSis^  are 
placed  on  the  most  secure  points,  beyond  the  range  of  the 
heavy  artillery  of  the  defences,  and,  If  practicable,  should  be 
hidden  from  their  view.  The  points  selected,  if  not  in  the  im- 
mediate neighborhood  of  the  ground  on  which  itjs  decided  to 
open  the  trenches,  should  have  avenues  of  easy  access  to  it,  for 
the  transportation  of  whatever  may  be  requisite  in  carrying 
forward  the  works  of  attack. 

62. ..Point  of  Attack.  After  obtaining  all  the  information 
that  can  be  had  from  the  reconnoissances,  surveys  and  other 
sources,  the  next  object  is  to  decide  upon  the  portion  of  the 
defences 'which  it  will  be  necessary  to  gain  possession  of  to 
force  the  garrison  to  surrender ;  this  portion,  usually  embrac- 
ing one  or  more  fronts  of  the  enceinte,  with  their  outworks, 
and  any  advanced  works  that  may  be-  connected  with  them, 
and  must  be  reduced  before  they  can  be  assailed,  is  termed  the 
J'o'mt  of  Attack.  It  is  in  the  choice  of  this  point — a  decision 
which  mainly  rests  with  the  commanding  officer  of  the  engi- 
neers— that  the  judgment  and  skill  of  this  officer  are  shown. 
In  making  this  selection, *he  must  carefully  weigh,  not  only  the 


ATTACK   AND  DEFENCE   OP    PERMANENT    WOBKS.  328 

relative  strength  of  the  various  points  of  the  defences  which 
arc  accessible,  hut  the  character  of  the  site  apon  which  the 
trenches  and  other  works  of  the  attack  most  be  lai<l  out,  and 
Che  facilities  of  an  easy  communication  between  the  park.-,  <h- 
pdts,  etc.,  and  the  point  selected. 

63. ..In  considering  the  strength  of  the  defences,  thoee  parts 
arc  regarded  as  unassailable  by  the  ordinary  measures  of  ad 
attack,  which  border  anon  precipices,  marshes,  fi  watei>cou 
that  cannot  be  forded,  or  arc  protected  by  works  on  inacd 
hie  points,  the  fire  from  which  swops  in  flank  and  reverse  the 
ground  over  which  the  trenches  must   be  run.    Those  p 
again,  are  considered  as  offering   peculiar  difficulties  which 
present  a  -eric-  of  works,  in  good  defensive  relation-,  which 
can  only  be  earned  in  succession;  or  which  arc  mine.];  or 
which  have  their  ditches  arranged  for  ■  play  of  water;  or 
which  have  dry  ditches  of  unusual  depth;  otV  finally,  where 
the  work.-  to  be  carried  arc  displayed  on  a  right   line,  embrac- 
ing the  same  extent  of  front  that   the   1"  can   take  up 
with  their  trenches.    The  bointa  which  are  becked  upoi 
most  advantageous  to  tin-  attack  are  those  in  which  the  general 
combination  of  the  works  foru             nt  point  with  respecfto 
the  rot  of  the  defence  bat 
little  support  from  the  collateral  portions;  can  be  enveloped 
l»v  a  line  of  trench  of  much  great  r  i  stent  than  itself,  a 
which  positions  can  1 btained  i'<<r  enfilading  and  other  bat- 
teries, the  fire  of  which  will                        'it   upon   that 
defei 

<il....\-   regards  tie  n  which   I  •  and  ol 

works  nm.-t  he  Laid  out,  the  diflicoltu 
straction  by  hare  rock,  marsh,  or  hard,  si 
readily  appn  »ver  can  only  be  had  on  I 

by  bringing  the  earth  from  a  '  te  para] 

dik-  md  <»n  the  la- 

the trenches,  and  the  add  I     l 

troops  from   the  Ira 
by  the  shot  ol  tin 


3l'4-         attack   \m»  defence  of  permanent  works. 

are  others  less  obvious  which  should  be  taken  advantage  of  or 
be  avoided,  as  favprable  or  otherwise  to»the  construction  of 
the  work*  of  the  attack.  A  surface,  for  example,  which  slopes 
or  falls  away  toward  the  defences,  if  commanded  by  them,  is 
unfavorable  both  to  the  construction  of  trenches  and  batteries; 
fee,  "to  gain  sufficient  cover,  both  the  parapet  and  trench  will 
have  to  receive  dimensions  greater  than  under  ordinarj  cir- 
cumstances; and  the  defilement  of  approaches  will  also  be 
easily  effected.  A  surface  which  rises  toward  the  defenc< 
verv  favorable,  both  for  gaining  cover  speedily  and  for  defiling 
with  advantage  the  approaches;  but  is  less  so  as  a  site  for  bat- 
teries if  the  slope  is  rapid.  An  undulating  surface  may  offer, 
in  some  points,  natural  covers,  and  be  at  other  points  favorable 
as  sites  for  batteries  ;  this  will  depend  upon  the  position  ot  the 
undulation  of  the  surface  with  respect  to  the  lire  of  the  de- 
fences. A  ridge,  for  example,  leading  out  from  the  defences, 
whilst  it  would  present  a  cover  to  the  works  on  one  side  of  it 
from  the  fire  of  the  defences  on  the  other,  would  expose  the 
trenches  on  the  other  side  of  it  to  a  plunging  fire  from  the 
same  points. 

'A  narrow  valley,  similarly  placed,  would  he  verv  unfavor- 
able, as  both  of  its  sides  would  be  exposed   to  a  plunging  lire. 

Seconh  and  Tm in)  Periods. 

65...Plan  ami  Journal  <>f  the  Attack.  The  plan  of  the 
attach  is  necessarily  based  upon  the  character  of  the  defences 
of  the  point  of  attack,  and  of  the  site  upon  which  the  ap- 
proaches and  other  works  of  the  besiegers  must  be  laid  out; 
and  by  this  term  is  understood  both  the  means  to  he  used  at 
the  successive  stages  of  the  operations,  and  the  disposition 
given  to  the  trenches  and  other  works.  The  journal  of  the 
attack  is  a  record  of  th%  daily  operations  of  the  besiegers;  and 
is  also  a  method  in  use  among  engineers  to  estimate  the  dura- 
tion of  a  siege,  from  the  opening  of  the  trenches  to  the  reduc- 
tion of  the  work,  on  the  supposition  that  the  works  of  the 
attack  can  be  Carried  on  regularly,  without  interruption  from 


ATTACK   AND   DEFENCE   OB    IM.KM  \  \  l\T    VfOQBB,  325 

unforeseen  contingencies:  a  method  of .  valuation  which,  as  it  is 
based  on  the  time  required  to  construct  a  given  amount  of 
work.  a>  determined  both  from  data  furnished  by  actual  b!< 
and  the  results  of  experiment  in  schools  of  practice,  may  be 
relied  on  as  an  approximation  as  elose  as  the  case  admits;  and, 
when  applied  in  a  spirit  of  fairness,  may  senre  il  B  leaf  of  the 
comparative  strength  of  different  combinations  or  systems  of 
permanent  works. 

66.. .The  general  disposition  of  the  works,, of  the  I  rs  is 

laid  d<»wn   on    the   map.  made  of  the  defences  and  envil 
with  ae  i  i-'.i<\  as  ean  be  insured  by  survey-  carefully 

made;  and,  from  the  results  obtained  in  this  way,  the  offi 
charged  with  this  duty  are  enabled  to  set  out  on  the  ground 
the  necessary  points  by  which  those  charged  with  directing 
the  construction  of  the  works  are  guid*  d. 

•  ;7....\>  an  illustration  of  the  plan  and  journal  of  attack.  We 
shall  suppose  the  point  af  attack  selected,  PL  l_.  Fig.  1, 
to  be  an  acute  bastion  With  the  two  adjacent  demilunes;  and 
that  the  only  collateral  works,  the  fire  of  which  bi  art  on  the 

ground  over  which  the  trenches  must  be  run,  are  two*  coll) 

al,  obtuse  bastions,  the  faces  of  which  cannot  be  enfll* 
owing  to  their  prolongations  falling  within  the  salient 
adjacent  demilunes,  and  the  two  collateral  demilunes ;  making 
in  all  one  bastion  and  two  demilunes,  with  tJieii  dent 

outworks,  which  must  he  entered  by  breach  oi  otherwise]  and 
two  bastions  and  two  demilunes,  with  their  dependent 
the  tire  of  which  must  be  kept  under. 

'  -     :  aches  will  be  pushed  forv  I  ion 

of  the  capitals  of  the  thn  • 

parallels  will  embrace  a  sufficient  front  to  incJ  prolon- 

gations of  tie  ;'  all   tie 

inst  which  enfilading  l»at 
■  ..The  first  parallel  will  bi 

OlOSt    a'i  |]|<  1 

nearly  to  the  lin< 

which  lead  from  it  to  th< 


326  ATTACK    AND    I>1"1  1  N»  B    OP    ITKMAM  NT    WORKS. 

zig-zags  across  the  capitals,  each  not  over  100  yards  in  length, 
and  defiled  from  the  most  dangerous  points  within  cannon 
range. 

7"... I'ii:-t  NlGHT,  The  position  of  the  portion  of  the  trenches 
apon  which  tlie  besiegers  are  to  break  ground  having  been 
laid  <>ut.  and  the  materials  for  the  wyrk  having  been  placed  in 
order  for  distribution,  so  as  to  avoid  all  unnecessary  delay  and 

contusion,  the  workmen  arc  assembled  at  the  depots  of  the 
trenches  before  night-fall  to  receive  their  Implements.  The 
men  selected  for  this  duty  are  troops  of  the  line,  who  usually 
take  their  arms  with  them.  The  men  are  divided  into  work- 
ing  parties,  each  of  which  is  under  the  command  of  an  office*1 
of  the  line,  and  they  are  marched  in  single  file  by  a  Hank  and 
posted,  after  night-fall,  where  they  are  to  work  under  the  di- 
tion  of  the  engineers. 

The  portion  of  the  trenches  opened  this  night  are,  usually, 
only  the  approaches  that  lead  from  the  depots  of  the  trenches 
to  the  first  parallel,  and  that  portion  of  this  parallel  which  em- 
braces the  capitals  of  the  point  of  attack.  To  guard  the  work- 
men from  sorties,  as  many  battalions  of  the  line  as  may  he 
requisite,  termed  thegiwzrds  <>fl/i<  trenches^  are  thrown  forward 
about  30  paces  in  advance  of  and  on  the  Hanks  of  the  men  who 
open  the  first  parallel.  The  ilank  companies  of  these  batta- 
lions, divided  into  sections,  cover  the  front  of  the  battalions, 
and  are  posted  about  30  paces  from  them;  and  each  section 
posts  two  sentinels  at  about  the  same  distance  to  its  front.  The 
sentinels  keep  a  look  out,  kneeling  on  on.-  knee  ;  the  remainder 
of  the  troops  lie  flat  on  the  ground  to  avoid  the  lire  of  the  de- 
fences. 

When  the  working  parties  are  all  posted,  the  men  of  each 
lying  flat  until  all  are  ready  to  commence  the  work,  the  order 
is  given  to  rise,  ground  their  arms  a  few  paces  to  the  rear,  and 
break  ground. 

The  guards  of  the  trenches  keep  their  position  until  near 
dawn,  when  they  are  withdrawn  and  take  post  in  the  parallel, 
which,  by  this  time,  will  be  nearly  excavated  to  its  full  width. 


ATTACK   AND  DEFENCE!   OF    PJ  i:\IA\l  XT    WoIiKS.  327 

On  the  succeeding  day  all  that  remain.-  to  be  done  to  the 
trenches  opened  is  completed,  and  everything  is  gol  in  readi- 
ness for  the  work  of  the  coming  night, 

71...Si «  mm.  Night.  The  parallel  will  be  extended  this  night 
to  embrace  the  prolongations  of  all  the  laces  to  be  enfiladed, 
and  some  100  or  150  yards  beyond  the  extreme  points  so  <1«- 
lermined.    A  large  square  redoubt  will  be  constructed  at  each 

extremity    of  the    parallel,    which    will    be    armed    \\\\}]    field 

pieces;  and  an  epaulment  for  cavalry  will  be  thrown  hp  in  the. 
rear  of  each  redoubt  i  the  object  of  these  works  being  to  con- 
tain troops  to  act  against  sorties  made  on  the  flanks  of  the  par- 
allel 

The  zig-zag  approaches  are  pushed  about  160  yards  in  ad- 
vance of  the  parallel.  The  positions  of  these  approaches  are 
determined  on  the  plan  by  setting  off  points  cm  the  first  paral- 
lel at  80  yards  on  each  side  of  the  capital,  and  drawing  I 
from  each  of  these  points  to  corresponding  point!  about  15 
yards  on  the  side  of  the  capital,  at  the  salieni  of  the  covered' 
way.  then  limiting  the  length  of  each  zig-zag  ofthi  »,  the 

direction  of  each  depending  on  its  defilement.  To  cover  more 
completely  the  rev<  fee  of  each  zig-zag,  and  secure  it  from  i 

tinii.-  that  mi^ht  be  taken  up.  e\teri..rt<.  the    defei  •  nli- 

lade    it.    the   zig-zag    in    advance    should    be    prolonged    back 

beyond  the  limiting  lines  a  d  ■  :'  LO  or  12  yard-  to 

rear  of  the  one  immediately  behind. 

72.. .R]  m\kk.    It  maj  rved  here  that  by  running  ap> 

proaches  upon  three  capitals,  we  not  only  multiply  the  lin< 
communication  between  the  parallels,  but  divide  the  attention 
of  the  b<  The  lines  of  the  capitals  are  also  the  i 

suitable  for  '  (junta  :  first,  * 

the  short*  st  n  the  parallels  and  t! 

within 
the  angle  formed  by  the  prolong] 

re  of  tii. 
oft) 


328  ATTACK    AND    DHFKNc:'    OF    IT.KM  AN'I'NT    WORKS. 

tliis  position  the  approaches  arc  nmre  easily    defiled   from   the 
collateral  fire  than  in  any  other. 

By  confining  the  zig-zags  within  the  lines  drawn  from  the 
parallel,  and  converging  toward  the  salients,  the  front  6i  each 
approach  is  gradually  eontraeied  as  it  nears  the  salient,  and 
offers  less  obstruction  to  the  fire  of  the  parallel. 

73. ..The  trenches  and  other  works  left  incomplete  at  the  end 
of  the  second  night  are  finished  on  the  following  day;  and 
this  rule  is  followed  throughout,  as  the  trenches  Commenced 
by  night  are  generally  in  a  suitable  state  by  dawn  t<>  give 
cover  to  the  workmen  and  troops',  and  can  be  occupied,  and 
what  remains  to  be  done  to  them  be  completed  in  safety  by 
day. 

74. ..Third  Night.  The  approaches  are  pushed  forward  275 
yards  from  the  first  parallel,  and  here  the  second  parallel  is 
commenced;  a  small  portion  of  it  only  on  each  side  of  the  ap- 
proaches being  opened,  in  which  to  lodge  a  few  troops  for  the 
protection  of  the  workmen. 

This  parallel  is  of  less  extent  than  the  first,  embracing  only 
the  prolongations  of  the  faces  of  the  point  of  attack.  It  is 
usually  connected  with  the.  first  parallel  by  a  defiled  line  of 
trench  at  each  of  its  extremities.  Its  distance  from  the  first 
is  determined  from  the  consideration  that  the  workmen  em- 
ployed on  it  must  be  protected  by  the  guards  of  the  trenches, 
who  are  still  stationed  in  the  first,  and  who,  to  afford  this  pro- 
tection, should  be  posted  where  they  can  come  to  the  aid  of 
the  workmen  before  the  garrison  can  reach  them  in  a  sortie. 

The  rule  here  observed  is  also  a  general  one.  The  trenches 
under  construction  never  in  any  case  being  advanced  so  far 
that  the  guards  in  their  rear  cannot  come  up  to  their  support 
before  they  can  be  reached  by  a  sortie  from  the  defences. 

75. ..Fourth  Night.  The  second  parallel  is  entirely  laid  out 
on  this  night,  and  is  completed  on  the  following  day.  The 
guard  of  the  trenches  takes  post  in  the  parallel  as  fast  as  a 
part  of  it  is  finished;  a  reserve  equal  to  about  one-third  of  the 
whole  being  left  in  the  first  parallel. 


ATTACK    AND   DKFK.Wi;    OF    I'KKMAM.M     WOKSBk  829 

As  the  second  parallel  is  at  325  yards  from  the  salient  of  the 
place,' the  workmen  arc  much  eiposed  to  the  fin  of  grape 
shut:  it  will,  therefore,  be  necessary  to  use  the  flying  >a]»  in 
its  construction. 

7<;...I''i![ii  ami  Sixth  Nights.  Thus  far  the  works  of  the 
attack  have  been  pushed  forward  without  the  aid  of  artillery, 
but  beyond  the  Becond  parallel  the  fire  of  the  defences  1m- 
comes  so  destructive  that  farther  progress  cannot  be  made, 
without  great  sacrifice  of  life,  until  it  is  silenced.  To  effect 
tins,  enfilading,  mortar  and  counter-batteries  are  plaeed  about 
30  yards  in  front  of  the  parallel.  The  number  of  gun*  in  each 
battery  will  depend  on  the  importance  of  the  face  to  be 
silenced,  and,  according  to  tin's  rule,  the  following  distribution 
will  be  made  :  ' 

A  battery  of  8  pieces  will  be  erected  against  each  face  of  the 
bastion  of  attack.  A  battery  of  5  pieces  againBt  tin-  right 
tare  of  the  demilune  of  attack  and  it.-  covered-way,  and  one  of 
7  pieces  against  the  left  fao  the  fire  from  the  Latter 

bean  more  directly  on  the  approaches  than  that  of  the,  right 
face.     A.-  the  two  collateral   bastions  arc  supposed  t<>  be  so 
obtuse  that  their  feces  cannot  be  enfiladed,  it  will  be  necessary 
to  silence  their  fire  by  counter-batteries.     As  the  left  face 
alone  of  the  bastion,  on  the  right  of  the  one  of  attack,  b« 
direct  action  on  the  approaches,  a  counter-battery  of  •' 
is  erected  against  it.  and  so  placed  as  to  obtain  a  slant 
into  its  embrasures.     With  regard  to  the  collateral  demilune 
on  the  same  side,  as  its  right  face  has  but  a  slight  bearing  on 
the  approaches,  a    batters  of  '■'<   < 
from  being  occupied  l>y  the  I 
its  lj  t,  it  will  De 

battery  of  5  pi<  battery  i  in 

1r«.nt  of  the  first  parallel.     Two  or  thr<  part 

h  battery,  t  and  dit< 

The  ne. nar  batteries  are  plac<  d  in  posit 
be  most  effective,  which  i.-  usuallj 
capitals  of  tl 


330  ATTACK    AND    DEFENCE   OF    PERMANENT   WOKKS. 

t:u>  arc  placid  in  eaoh  battery,  an  allowance  of  8  mortars 
being  made  for  each  front  embraced  by  the  trenches. 

The  mortar  and  gun  batteries,  the  fire  of  which  is  not  ob- 
Btructed  by  the  trenches  in  front  of  them,  are  snnk.  The  plat- 
forms of-the  others  are  on  the  natural  surface  of  the  ground. 

Besides  these  Latteries,  which  will  he  completed  on  the  tilth 
and  sixth  nights,  two  or  three  zig-zags  are  pushed  forward  in 
advance  of  the  parallel  on  the  same  nights,  if  the  lire  of  the 
besieged  is  not  too  destructive. 

77. ..Si  \  i. viii  Nl&HT.  As  the  enfilading  batteries  will  he 
Completed  and  armed  on  the  sixth  night,  on  the  following 
morning  they  will  all  open  their  fire  at  the  same  moment,  and 
by  night  the  lire  of  the  place  will  he  nearly,  it'  not  entirely, 
silenced."  The  approaches  are  then  pushed  forward,  and  demi- 
parallels  are  established  at  from  100  to  150  yards  in  front  of 
the  second  parallel.  The  demi-parallels  may  be  from  100  to 
200  yards  in  length,  and  have  a  return  of  25  yards  at  their 
extremities  to  cover  them  on  the  flank.  The  length  of  the 
demi-parallel  should  he  so  regulated  as  not  to  obstruct  the  fire 
of  the  ricochet  batteries.  In  some  cases  howitzers  are  placed 
in  batteries  established  at  the  extremities  of  the  demi-parallels, 
to  enfilade  the  covered-ways;  but  as  the  demi-parallels  are 
within  good  musket  range  of  the  covered-ways,  it  will  gener- 
ally he  better  to  arm  them  with  infantry,  the  top  of  their  para* 
pet  being  arranged  with  loop-holes  made  with  sand-hags,  to 
cover  the  marksmen  whilst  in  the  act  of  firing. 

78...Ei(.inu  Niuiit.  On  this  night  the  approaches  are  pushed 
forward  by  the  Hying  and  full  sap,  as  opportunity  may  offer, 
and  a  portion  of  the  third  parallel  is  commenced  when  the  ap- 
proaches are  within  0<>  yards  of  the  most  advanced  salients. 

79...i\i.vni  Night.  The  third  parallel  is  completed.  It 
should  present  a  less  development  than  the  second,  so  as  to 
be  flanked  by  it,  and  will,  therefore,  usually  embrace  only  the 
salients  of  the  point  of  attack.  Owing  to  this,  and  its  having 
to  receive  the  main  body  of  the  guard — the  second  parallel 
now  containing  only  the  reserve,  whilst  the  first  is  used  only 


ATTACK    AND    Mil  \.  E    OF    PERMANENT    WOBM.  331 

as  a  depot  for  the  materials  and  to  receive  the  wounded — the 
third  parallel  is  made  two  ox  three  feet  wider  than  the  other 
two. 

S0...U1  m akk.  With  the  completion  of  this  parallel  begins 
the  third  and  last  period  of. the  attack.  At  this  point,  the 
works  of  the  besiegers  are  necessarily  contracted  to  a  very 
narrow  front,  and  present  but  little  more  development  than 
that  of  the  point  of  attack:     They  are  now  upoii  the  immediate 

gVOnnd   of  the    defences,    and    within  range  of  every  mean-  of 
annoyance.      In  pushing  forward  from  this  position  the  besi 
era  are.  to  a  great  decree,  deprived  of  the  assistance  that  they 
hitherto  had  from  their  enfilading  and  other  hat:  the 

position  of  their  trenches  on  the  glacis  musl  obstruct  this  fire; 
they  can  no  longer  use  the  Big-cag  approach,  hnt  I  gain 

ground  by  the  doable  sap.  and  soon  find  themselves^  as  their 
works  advance  toward  the  re-euterings,  the  enveloped  instead 
of  the  enveloping  party,  and  liable  at  every  moment  to  have 
their  sappers  cut  off,  and  their  labor!  Btopped  by  sorties  in 
small  parties.  It  is  at  this  stage, then,  that  more  than  ordinary 
precautions  are  requisite,  not  only  to  prevent  retardation  of  the 
works,  but  to  avoid  unnecessary  sacrifice  of  life;  by  preparing 
all  possible  mean-  for  insuring  the  sue  I   p.  and 

by  not  advancing  on  one  until  the  last  taken  is  perfectly  secure. 
BL..Tcm    Nnon.     A-  the  third   parallel,  PL  12,  Fig.  1. 
from  it-  position  on  tl  -.  will  mi 

(diet  batt  ■  /■'.  it  will  he  i 

establish  new  ball  n  front  of  it.  to  dislodge  the  besi<  _r-'d 

from  this  outwork.     For  this  pur] 
are  found  very  sffectn  e.    These  b  l   about 

90  yard-  in  trout  of  the  parallel,   and 

4  or  6  mortar-  i-  placed  on  ea  in 

the  prolonged  direction  of  1 

will  he  ready  to  C  'li  the    C 

the  morning 
completion   of  tie    third 


ATTAf  K    AND   DEFENCE   OF    PERMANENT    WOBKS. 

crowning  the  covered-way;  either  by  storm  <>r  by  gradual  ap- 
proaches. In  tin*  former  case,  portions  of  the  parallel  arc  ar- 
ranged with  steps  to  enable  infantry  to  sally  from  it  on  the 
covered  ways.  The  sappers,  with  all  the  w  cessary  materials 
for  crowning  the  covered-Way,  arc  collected  in  the  parallel. 
At  a  preconcerted  signal,  a  lire  will  be  opened  from  the  stone- 
mortar  batteries,  ami  all  others  that  arc  still  effective,  against 
the  covered-way  and  the  other  outworks.  When  it  is  per- 
ceived that  tin-  fire  has  produced  its  effect  in  clearing  the  out- 
works, at  a  preconcerted  signal  it  will  also  cease  ;  the  troops 
will  sally  forth  and  carry  the  covered-way  with  the  bayonet, 
and,  after  gaining  possession  of  it,  they  will  shelter  themselves 
as  best  they  can  behind  the.  traverse  from  the  tire  of  the  be- 
sieged. ^Whilst  thev,  in  this  way,  maintain  possession  of  the 
covered-way,  the  sappers,  who  follow  immediately  in  their 
rear,  will  open  a  trench  about  4  or  5  yards  from  the  crest  of 
the  glacis,  around  the  salient  place  of  arms,  as  tar  as  its  two 
traverses;  when  this  trench  will  afford  a  shelter  to  the  troops, 
they  retire  from  the  covered-way  into  it.  This  trench  is  after- 
wards connected  by  suitable  communications  with  the  third, 
parallel. 

From  the  circumstances  under  which  this  operation  is  car- 
ried on,  the  probabilities  are  against  its  success  and  in  favor  of 
a  great  sacritice  of  life  in  the  attempt,  if  the  besieged  offer  a 
vigorous  resistance  and  make  a  skilful  use  of  the  means  still  at 
their  disposal.  With  such  chances,  therefore,  of  failure,  and 
the  certainty  pf  great  losses  even  if  successful,  this  mode  of 
attack  should  only  be  resorted  to  in  some  contingency  where 
the  success  of  the  siege  depends  on  the   time  saved  by  it. 

83... fa. i  \  i  viii  NlQHT.  When  the  covered-way  is  to  be 
crowned  by  regular  approaches,  a  constant  lire  is  kept  up  from 
the  stone-mortar  batteries  so  as  to  render  it  untenable  for  more 
than  a  very  few  men,  A  trench,  termed  the  oirotdew place  of 
arms,  is  now  formed,  by  starting  from  two  points  of  the  paral- 
lel at  30  yards  on  each  side  of  the  capital,  and  pushing  two 
I  tranches  of  full  sap  to  unite  at  about  15  yards  from  the  paral- 


ATTACK    AND    DEFENC1     01     l'l  KMA  NKM    Woi, 

lei,  on  the  capital.  From  this  point  a  doable  sap  is  poshed 
along  the  capital,  to  within  80  yards  of  the  clients  ol  the  dem- 
ilune coveredrways.  As  the  bastion  covered-wa^  is  very  he- 
tired,  nothing  more  is  done  than  to  form  the  circular  place  of 
anus  before  it. 

84...Twi  i. iin  Night.  The  trench  cavaliers  before  the  demi- 
lune salients  arc  commenced,  and  the  sap  Lb  pushed  forward  a 
few  yards  on  the  bastion  covered-way. 

85...Tmi:i r.i  vin  Nimm.  The  trench  cavaliers,  which  require 
from  36  to  48  hours  for  their  completion,  will  be  finished  on 
this  night,  and  an  approach  pushed  from  the  stone-mortar  bat- 
teries toward  the  reentering  place  of  arms. 

80...F<«rini  i  n  in    Xionr.     The   besieged    being  now   driven 
from  the  covered-wayi  by  the  fire*  of  the  trench  cavaliers,  :i 
double  sap  is  pushed  toward  the  salient  of  the  demilnne  < 
ered-way  from  the  two  extremities  of  the  circular  trench  con- 
necting the  trfeoch  cavaliers.    Thesis  two  saps  unite  at  1  ■ 
yards  firom  the  crest  of  the  glacis. 

The  approaches  toward  the  reentering  place  of  arms  are  ad- 
vanced farther  on. 

-  7 ...  I  1 1  1 1 1  vi  ii  N  toHTi  Hie  demilnne  covered-way  is  crowned 
Ear  as  the  leebnd  traverse.     The  approaches  on  the  reenter- 
mg- place  of  .-inns  and  the  salient  of  the  bastion  covered-way 
ire  advanced. 

-  ...A  fourth  parallel  is  began  on  this  night,  c 
opposite  the  first  traV<  rses  of  the  demilune  eov<  red-ways,  and 
uniting  the  approacl  d  toward  the  r<  Sntering  i 

arms. 

v'.'...Si\m  i  mii    Ni'.in.    The   breach   and    cuunter-1    tl 
around  the  salient  pis  demilni 

and  armed. 

From  1  to  5  guns  will  be  placi  d  on  each  branch  of  • 
of  the  salient  place  of  arms,  in  the  j,, 
lune  ditch,  to  count,  r-batter  the  port 
which  hear  upon  this  ditch  and  t 

this  tire  troiu  retard;;..'  Hie  lodgn 


334:      ATTACK  AND  DEFENCE  OF  PKHMANKNT  "WORKS. 

tcrreplein  of  the  salient  place  of  arms  and  the  passage  of  the 
•litch.  About  4  guns  are  placed  in  a  battery  between  the  first 
and  second  traverses,  to  open  a  breach  in  the   left  face   of  the 

demilune.  This  breach  should  be  from  20  to  3<>  yards  in  width, 
and  not  extend  farther  toward  the  salient  than  the  position  of 
the  pancoupe,  so  as  to  expose  as  great  an  extent  of  the  interior 
of  the  demilune  as  practicable. 

The  guns  in  these  batteries  will  require  cover  in  flank  from 
the  faces  of  the  bastions  and  their  cavaliers ;  and  in  rear  from 
the  most  advanced  salients  of  the  works  still  occupied  by  the 
besieged, 

The  descent  into  the  demilune  covered-way,  commenced  on 
the  fifteenth  night,  behind  the.  first  traverse,  is  finished;  and 
the  fourth  parallel  is  completed.  The  width  of  the  fourth  par- 
allel is  the  same  as  an  ordinary  approach,  owing  to  the  diffi- 
culty of  defiling  it. 

These  batteries  will  be  completed  and  armed  in  24  hours 
after  the  crowning  is  commenced.  The  breach  will  be  prac- 
ticable in  12  or  15  hours  after  the  tire  is  opened. 

0O...Seventeenth  Xk.iit.  The  approaches  from  the  fourth 
parallel  are  pushed  forward  on  the  salients  of  the  bastion  cov- 
ered-way and  the  reentering  place  of  arms.  The  crowning  of 
the  demilune  covered-way  is  gradually  advanced  and  a  lodg- 
ment is  made  on  the  terreplein  of  the  demilune  salient  place  of 
arms,  from  which  the  demilune  ditch  can  be  swept  by  mus- 
ketry. 

The  descent  into  the  demilune  ditch  is  commenced  on  this 
night,  behind  the  traverse  of  the  salient  place  of  arms. 

(Jl...In  advancing  the  sap  on  the  different  salients  of  the 
covered-way,  from  the  fourth  parallel,  care  should  be  taken  not 
to  push  forward  one  faster  than  the  others,  so  as  not  to  oiler  a 
temptation  to  the  besieged  to  sally  out  on  the  head  of  the  most 
advanced,  to  cut  oil'  the  sappers.  Moreover,  the  different 
brigades  of  sappers  should  be  protected  by  a  few  picked  men, 
stationed  in  short  trenches  that  ilank  the  direction  of  the 
double  sap  as  it  is  pushed  forward  on  the  salients. 


ATTACK   AND    DEFENCE   OF   PERMANENT    Woi:k>.  335 

92. ..If,  owing  to  the  great  width  of  the  covered-way,  or  to 
the  small  breadth  of  the  demilune  ditch,  or  to  the  steepm 
the  glacis,  by  which  the  batteries  placed  along  its  creel  woald 
be  very  much  exposed  to  a   reverse  fire  from  the  collateral 

works,  it  shtould  become  necessary  to  place  the  breach  ;m<l 
counter-batteries  on  the  terreplein  of  the  covered-way,  they 
cannot  be  completed  and  armed  before  the  seventeenth  ot 
eighteenth  night.  Although  the  batteries  in  this  position 
would  l>e  well  covered  from  reverse  five  by  the  creel  of  the 
glacis,  and  tiv.ni  a  think  lire  by  the  traverses  of  the  eovered- 
way,  still,  they  would  require  much  more  labor  to  establish 
them,  and  would  be  more  exposed  to  the  annovanee  of  gre- 
nades thrown  from  the  demilune. 

After  the  descent  into  the  demilune  ditch  is  commenced,  it 
is  steadily  carried  forward  until  it  arrives  at  the  point  opposite 
the  breach,  where  the  opening  into  the  ditch  Lb  to  be  made 
through  the  counterscarp  wall;  This  opening  should  be  pierced 
at  night,  and  the  precaution  Aould  be  taken  to  run  a  small  gal- 
lery along  the  back  of  the  wall,  on  each  side  of  the  opening, 
so  as  to  plaeq  a  few  men  to  lire  through  loop-holes  made  in  the 
wall,  for  the  purpose  of  defending  the  opening,  and  the  sap 

|MlBhed  RCrOSS  the  ditch  to  the   breach. 

...K1..11 1 1  1  Mil,  Nineteenth  and  Tu  i  \  m  m   Nighti 
approaches  from  the  fourth  parallel  and  the  crowning  of  the 
sovered-way  are  pnshed  forward  and  completed  on  these  nia 

It  will  seldom  be  practical.  abliifa    a  trench    cavalier 

against  the  bastion  salient  place  of  arms,  owing  to  thi 

tire  from  the  collateral  demilune-.     In  luch  a  ease,  it'  the  be* 

d   still  occupy   this  work    in   foi 
progress  of  I  pi  must  be  made  to  dislodj 

by  an   open  attack   of  a  small  party  of  picked  tr< 

stone-mortar  batti  ay  be  placed  iu  the  position  that  would 

be  occupied  by  the  trench  i  .  by  means  of  which 

ged  may  be  driven  from  this  pail 
So  'lie  bastion  cover*  d-way  i.-  crowi 


'■'<'■'>>',  ATTACK    AND    I'll  I. Mi:    OF    lTUMAMNl     WOStfB. 

arc  commenced  into  tile-maid  ditch,  from  the  trench  at  the 
salient  <>t'  the  covered-way. 

In  very  acute  bastions,  the  breach  and  counter-batteries 
along  the  bastion  covered-way  might  be  completed  on  the 
twenty-first  night.  But,  generally,  before  this  can  be  done 
the  demilune  must  be  carried,  as  its  tire  would  take  these  bat- 
teries BO  in  reverse  as  to  render  their  construction  impracti- 
cal ik-. 

<J-4...T\vi:n  i  v-i-iitii    XiNirr.     The   descent    into    the  demilune 

ditch  and  passage  of  the  ditch  may  he  effected  by  this  nighl  at 
farthest. 
Every  precaution  should  he  taken  to  prevent  the  besieged 

from  interrupting  this  passage.  The  passage  itself  should  he 
4  or  5  yards  wide  at  bottom,  to  afford  a  convenient  place  of 
arms  for  the  troops,  and  it  should  be  arranged  with  a  banquette 
to  sweep  the  ditch  by  a  close  musketry  fire. 

Besides  making  loop-holes  in  the  counterscarp  wall  to  flank 

the  passage,  it  will  also  he  Well  to  push  forward  one  of  two 
zig-zags  in  the  ditch  itself,  and  place  a  small  party  of  picked 
men  in  them  to  repel  the  sorties  of  the  besieged, 

95^..The  breach  is  gained  possession  of  either  by  storm  or  by 
gradual  approaches.  The  former  will  he  resorted  to  when  the 
besieged  manifest  a  determination  to  keep  possession  of  the 
demilune,  in  force,  to  the  last  extreiuitv.  A  few  Companies  of 
picked  men  will  he  chosen  for  this  service.  All  the  materials 
will  he  collected  at  hand  for  crowning  the  breach,  and,  when 
everything  is  in  a  state  of  readiness,  a  warm  lire  will  he  opened 
on  the  breach  and  on  all  the  works  that  in  any  way  hear  upon 
it.  At  a  preconcerted  signal  the  fire  will  cease,  and  the 
assaulljing  column,  rnshing  through  the  breach,  will  drive  the 
besieged  from  the  demilune,  and  then,  sheltering  themselves 
as  they  best  can  from  the  tire  of  the  other  work,-,  they  will 
maintain  possession  of  the  breach  until  the  sappers,  who  follow 
in  their  rear,  can  effeel  a  Lodgment  on  its  top. 

'.m;...Tu  make  the  lodgment  hv  gradual  approaches,  the  sap- 
pers will  push  forward  a  sap  from  the  foot  of  the-  breach,  over 


AT'fcW'K     AM.    T>1  I  I   \<    I      OF     IMKMWIM      WdHKI.  337 

the  ruin?,  giving  if  nicb  a  direction  as  to  gain  a  shelter  under 
the  end  of.  the  wall  that  remains  on  tin-  side  of  the  breach 
which  is  exposed  to  the  fire  of  the  besieged.  A?few  picked  men 
•will  cautiously  mounl  to  the  summit  of  the  breach,  occupying 
such  sheltered  points  as  may  be  found  at  hand,  for  the  pur- 
of  covering  the  sappers  whilst  at  work.  These  men  will 
be  sustained  by  a  detachment  posted  along  the  pa  the 

ditch. 

!<7...T\\  i  n  i  Y-i\  i ii  Night.    The  lodgment   on  the  breach  of 
the  demilune  being  effected  on  tins  night,  the  breach  :m<l 
counter-batteries  along  the  bastion  covered-way,  and  against 
the  redoubt  of  tin-  reentering  place  of  arms,  can  be  eompli 
and  armed. 

A  breach  battery  of  1  guns  will  be  placed  along  cadi  c 
of  the  bastion  covered-way,  as  far  from  the  salient  as  room  can 
be  had,  for  the  purpose  of  opening  as  wide  a  breach  as  practi- 
cable at  the  bastion  salient.     A. counter-battery,  like.' 
guns,  will  be  placed  along  the  same  crest,  and  in  the  best  p 
tion  t<»  fire  in  the  prolongation  of  the  main  ditch  and  bUi 
the  fire  of  the  enceinte  flanks  opposite  to  them.     A  ln-cach 
battery  of  3  guns  will  also  be  placed  each  of  the  re- 

doubts of  the  reentering  place  of  arm.--,  to  oj.cn  them  on  their 
lace-  thai  lie  adjacent  to  the  dcmilunt 

These  bal  ■!  in  Hank   and   rear  in  the  same 

manner  as  against  the  demilune. 

I  from   attempting 
besiegers  from  the  demilune,  it  is  well  to  ict  a  trei 

acrof  •  from  which  the  ditch  of  the  demilnm 

doubt  can  be  swept   by  a  fire  of  musketry,     I 
be  made  on  tic  i  th  night. 

►on  a-  the  <i>  iiiilwne  breach  : 
commenced frotu  the  lodgment  on  it  t  ibt 

until  the  thitf  d  night 

In    tin- 

43 


338  .attack   am>  DEFENCE  Of  i'i:i;mam:m   wokks. 

and  a  doable  Bap  be  formed  in  the  parapet  of  the  demilune  it- 
.  to  overlook  the  ditches  and  to  approach  the  cut  in  the 
demilune  face 

A  descent  can  also  be  made  on  or  before  the  thirty-second 
night  into  the  reentering  place  of  arms,  and  a  Lodgineift  he 
effected  on  itfe  terreplein. 

99.. .On  the  thirty-second  nighty  miners  arc  Bet  to  work  at 
the  scarp  wall  of  the  demilune  redoubt,  and  at  the  scarp  and 
counterscarp  walls  of  the  cut.  The  mines  may  be  complete. 1 
and  fired,  and  the  Lodgment  he  effected  on  the  breaches  by 
the  thirty-fourth  night ;  at  which  time  the  breach  in  the  redoubt 
of  the  reentering  place  of  arms  is  also  carried. 

l(i(). .."When  a  breach  can  he  opened  in  the  bastion  face 
through  the  opening  of  the  demilune  ditch,  the  zig-zags  in  this 
ditch  mav  he  pushed  forward  nearly  to  the  extremity  of  the 
ditch,  and  the  passage  of  the  main  ditch  opposite  the  breach  in 
the  salient  he  effected  by  the  thirty-third  night,  so  that  the 
breaches  ill  the  body  of  the  place,  and  those  in  the  redoubts 
and  the  cut  can  all  he  Carried  on  the  thirty-fourth.  But  when 
a  breach  cannot  he  made  in  the  face  of  the  bastion  through 
the  demilune  ditch,  and  it  is  deemed  advisahlc  to  make  one  ;it 
this  point,  it  will  he  tfecesfiary  to  carry  the  outworks  first,  and 
afterward  to  push  forward  the  sap  to  crown  the  glacis  of  the 
sinu'le  caponniere  in  the  demilune  ditch,  where  u  1. reach  bat- 
tery of  two  guns  may  he  established  ;  at  the  same  time,  a 
lodgment  is  made  behind  the  bastion  covered  face,  and  a 
breach  battery  of  4  guns  is  established  there.  These  Labors 
Will  require,  for  their  completion,  until  the  thirty-seventh 
Bignt;      In  the  meantime,  lodgments  are  effected   on  the  upper 

and  lower  terrepleins  of  the  demilune  redoubt,  and  in  its  para- 
pet, to  overlook  the  main  ditch,  ihe  double  caponnicivs  and 
the  tenailles. 

The  passages  across  the  main  ditch  are  also  completed,  the 
descenl  to  the  one  nearest  the  shoulder  angle  being  com- 
menced from  within  the  postern  of  the  redoubt  of  the  reen- 
tering place  of  arms. 


attack    \m>  mil  x.i    oi   rri:M\\!\i    \\.:,  339 

101...Tiiii:tv-i:i>.h nr  Niter.  The  lodgment  on  the  breaches 
in  the  bastion  will  be  effected  on  this  night,  and  a  descenl  be 
commenced  from  the  top  of  the  breach  to  the  ditch  of  the  cav- 
alier. 

1  "l'... Thirty-ninth  lssd  Fortieth  Nights,.  A  lodgment  will 
be  effected  on  the  bastion  terreplein,  and  a  breach  battery  of 
i  {guns  be  established  againsl  each  face  of  the  cavalier. 

The  breach  in  the  cavalier  and  the  descent  into  the  ditch 
will  be  completed  so  that  the  final  assault  may  be  made  on 
the  forty-first  night. 

DEFEM  i:. 

The  object  of  this,  like  the  preceding  section,  is  to  give  a 
succinct  detail  of  the  operations  of  the  garrison  during  the 
successive  .-■  the  attack,  supposing  the  works   which 

they  occupy  provided  with  everything  requisite  for  cond 
iiig  tin-  defence  vigorously. 

LQ3. ..During  the  investment,  the  garrison  will  resort  to  ev<  ry 
mean.-  for  cutting  off  parties  of  the  investing  cdrpe  which  ap- 
proach the  work  incautiously,  and  will  particularly  endei 
t«>  prevent  all  attempts  at  reconnottering.     About  one-thii 
the  garrison  will  l»e  kept  on  this  duty,  tal 
work   "luring  the  investment    and  as  long  after  as    they 
maintain  their  position  without  too  gi 

1 « '  1 ...  As  i '  riod  have  no  other  danger  to 

apprehend  than  a  si  id  nothii  but 

tillerywill  l»e  so  posted  ai  I 
most  service  in  I 
should  be  placed  in  6m  b  ^ach  flank,  and  mm 

ynore   on   th( 

lune-.  with  gi  any  at' 

two  or  three  he*  ,  with  lot 

in  barb<  W  of  tin 

lime-,  to  keep  reconi 

!".'■...  W  li.il'  \ i  : 


340  ATTACK     AMI     l'l  I  1  N<  1      >>!      IMI.'MAMNl     WoKKS. 

siegers  to  deceive  the  besieged,  relative  to  the  point  of  attack 
and  the  time  of  opening  the  trenches,  the  latter,  by  keeping  a 
strict  watch  on  all  the  movements  of  the  former,  are  usually 

enabled  to  ascertain  both  with  tolerable  certainty,  and  to  pre- 
pare themselves  accordingly.  So  soon  as  these  points  are 
known,  the  garrison,  >till  keeping  mi  the  alert  to  frustrate  all 
attempts  at  Bnrprise,  and  without  changing  in  any  respect  the 
artillery  already  in  position,  will  place  all  the  disposable  pieces 
in  reserve,  in  the  best  positions,  on  the  fronts  of  attack  ami 
the  collateral  works,  to  do  the  most  damage  to  the  laborers 
and  the  guard  of  the  trenches  before  thev  are  placed  under 
cover  in  the  first  parallel.  Fire-halls  will  he  thrown  outevery 
night  to  light  op  the  ground  and  ascertain  the  position  of  the 
laborers  and  troops;  ami,  so  soon  as  they  are  discovered,  a 
heavy  tire  of  grape,  etc.,  will  he  opened  on  them  from  all  the 
guns  that  can  be  brbtight  to  bear  on  their  position.  At  the 
same  time,  a  few  howitzers'  Will  keep  up  a  ricochet  lire  in  the 
direction  of  the  capitals  to  annoy  the  workmen  at  the  ap- 
proaches. 

After  an  interval  of  two  or  three  hours,  the  parapet  of  the 
parallel  will  he  proof  against  grape-fchot,  mid  then  a  lire  of  halls 
and  hollow  projectiles  will  he  commenced,  and  directed  both 
alonir  the  capitals  and  to  take  the  guards  and  parallels 
obliquely. 

106... Unless  the  garrison  is  very  strong,  or  the  besiegers  show 
a  want  of  proper  precaution  in  covering  their  laborers  by  a 
strong  guard,  sorties  cannot  he  ma<h'  at  this  period  of  the  at- 
tack with  much  prospect  of  success,  owing  to  the  distance  of 
the  parallel  from  the  defences.  The  most  that  ought  to  he  at- 
tempted will  be  to  make  soiHe  charges  of  cavatoy,  to  cause  the 
laborers  to  stand  to  their  arms,  and  thus  retard,  for  a  shorti 
time,  their  operations. 

K>7...AVhcn,  from  the  indications  without,  there  is  no  longer 
any  doubt  respecting  the  real  point  of  attack  selected,  all  the 
disposable  artillery  will  be  brought  forward  and  placed  in  bar- 
bette! in  the  best  positions  on  this  point  and  the  collateral 


AIT  A  ik     \\i>   DEFJEJfOE   09    imkmwivi    WtU&S.  -".11 

works,  for  sweeping  the  ground  over  wliich  the  (ranches  must 
be  pushed.  Tn  the  rneaiftime,  embrasures,  platforms  and  trav- 
ersed arc  prepared,  oil  the  most  suitable  positions  to  place  the 
artillery  under  shelter  so  soon  as  Che  enfilading  batteries  are 
comph  ted. 

108.. .The  following  armamenl  maybe  taken  as  a  mean  for 
this  period  of  the  defence :  Eleven  pieces  in  the  bastion  <>i  at- 
tack,  one  of  which  is  an  8-inch  howitzer,  firing  in  the  direction 
of  the  capital,  the  others  may  be  Is  or  34-pounders,  five  being 
placed  on  each  face. 

Seven  or  nine  pieces  of  like  calibre,  and  similarly  di 
may  be  placed  In  the  cavalier  of  the  bastion. 
•     Eleven  pieces  will  be  placed  in  each  demilune  of  the  attack. 
one  being  an  8-inch  howitzer  to  fire  along  the   •  ,   the 

others  12  or  18-pounders,  six  of  which  arc  placed  on  the 
that  bears  on  the  ground  opposite  the  bastion  of  attack  ;  the 
other  three  on  the  other  ' 

Five  pieces  of  heavy  calibre  on  tli  WW)  collat- 

eral bastions  which  bear  most  directly  on  the  trend 
their  flanks  which  bear  on   the  bastion  of  attack  should  i 
receive  four  pieces  near  the  angle  of  the  cm-tain. 

In  the  collateral  demilunes,  six  pieces  air  placed  on  th< 
alone  that  hear  on  the  trend 

the   precedii  n   8-inch  howitzers  should  be 

placed  in  th<  >int  of  attack  and  of  the 

two  collateral  froi  I — two  being  in  each  place  of  aru 
in  ricochet  along  the  c:n-  l  \l>ont  twenty 

be  distributed  along  the  cm-tain-,  and  in   tl 
doubts. 

The  pieces  on   the  fac<  -  which  are  enfila 
:  by  gabionade  tf 
two 
down,  and  the  parapet   l 

loo. ...\n  nninterrnpb 
of  the  I 


342  ATTACK    AND    DEFENCE    OF    I'KKM  ANKNT    WOKKs. 

commence  throwing  up  the  enfilading  batteries.  The  fire 
should  be  concentrated  on  a  few  of  the  principal  batteries 
rather  than  scattered  over  all,  because,  by  delaying  the  prog- 
ress of  these,  the  odiers,  if  the  besieged  act  prudently,  will  not 
opeil  their  lire  until  all  are  ready. 

llo.. .If  the  approaches  are  upl  well  defiled,  or  are  directed 
too  near  the  salients,  works,  termed  counter-approaches,  may 
he  made  from  the  covered-way  to  enfilade  them.  These  works 
are  usually  small  redan  Latteries,  placed  near  the  foot  of  the 
glacis  to  receive  the  artillery  in  reserve  not  required  for  the 
immediate  defence  of  the  work.  They  are  connected  with  the 
covered-way  by  an  ordinaiy  trench.  These  Latteries  are  kept 
armed  only  during  the  day,  and  are  protected  by  small  detach-, 
ments  of  about  50  men,  to  secure  them  from  surprise. 

111. ..During  this  period,  the  engineer  officers  and  workmen 
are  employed  in  organizing  the  point  of  attack  for  a  vigorous 
defence.  The  covered-ways  are  palisaded  with  care.  Tarn- 
hours,  or  blockdioues,  are  estal dished  in  the  salient  place  of 
arms,  and  also  in  the  reentering  places  of  arms,  if  there  are  no 
permanent  redoubts.  Similar  arrangements  are  made  in  the 
demilunes  which  have  no  redoubts;  and  interior  retrench- 
ments, cither  of  a  temporary  or  permanent  character,  are  made 
in  the  bastion  of  attack.  Easy  communications  are  established 
between  all  the  works. 

112. ..With  regard  to  the  portion  of  the  garrison  on  daily 
duty,  the  greatest  number  will  be  posted  in  the  defences  more 
immediately  threatened  by  the  besiegers.  About  40  men  may 
be  posted  in  each  salient  place  of  arms  of  the  point  of  attack, 
and  20  in  the  collateral  salients ;  about  80  in  each  reentering 
place  of  arms  of  the  same  point,  and  40  in  each  of  the  collat- 
eral ones.  Besides  these,  there  should  he  a  detachment  of 
about  10  men  in  each  demilune  of  the  point  of  attack.  The 
number  and  disposition  of  the  daily  guard  will  of  course  vary 
with  circumstances.  The  main  point  to  be  attended  to  isvthat 
no  part  of  the  work,  of  any  importance,  shall  be  left  without 
a  sufficient  force  to  hold  the  besiegers  in  check,  in  case  of  sur- 


ATTACK     AM"    HI  I  IN'   I      OF     ITI.'MWlNi     WOl 

prise,  until  support  can  be  obtained  from  the  main  body,  which 
last  should  lie  bo  distributed  as  to  be  able  t«»  earn  succor 
promptly  to  any  part  threatened  or  attacked.  « 

118.. .So  long  as  the  besiegers  are  beyond  musket  range,  tin' 
guards  in  the  covered-way  have  only  to  keep  on  the  alert,  ami 
to  send   forward  in  the  daytime  a  few   picked    men,  who  t 
advantage  of  any  shelter  to  approach  the  tren<  I  fire  on 

the  workmen  or  guards  who  are  exposed,  and  at  night  to  keep 
out  patrols  to  scour  the  ground  around  the  work  :  to  annoy 
the  workmen  when  an  opportunity  offers,  and  to  prevent  the 
approach  of  reconnoitering  parties.  So  soon  as  the  trenches 
are  pushed  forward  within  musket  range,  an  uninterniitted 
warm  fire  ojF-nausketry  is  kept  up  on  the  workmen  and  guards 
that  are  exposed,  some  8  or  ><>  good  marksmen  being  placed 
in  each  salient  tor  this  service. 

H4...Sortiea   may  he  made   with  more  chances  of  sui 
when   the   1  nnaencc   the   second   parallel,  as  the 

iruai'ds   of  the    trenches  in  the  first  parallel  ai  Dear  at 

hand  to  protect  the  workmen  as  during  the  construction  of  the 
trenches  up  to  this  point. 

The  detachment  tor  the  sortie,  consisting  of  3  or  tOO  infan- 
try, will  sally  from  the  coverecr-ways  to  attack-  the  second  par- 
allel on  one  or  both  flanks,  ami.  if  circumstam 
front.  Winn  the  workmen  are  put  to  flight,  instead  of  pursu- 
ing them  into  the  first  parallel,  the ^etachment  will  form  in 
battle  order  to  cover  a  party  1  hundred.-  of  work' 

who  follow  in   rear  of  the  detach  m<  nt  whilst   they  are  till- 
ing up  the  tn  in  roying  the  imp 
fire  to  the  gabions.     The  working  party  will  b< 
each  flank  by  a  detachment  of  infantry  and  all  tin 
ca\ airy  of  the  place.     Winn  the 
pear  in  force  to  repu  rtie  the  I 
without  compromising  tl  d  will  i 
the                   -  in  the  pursuit  within  <h..rt    I 

of  which  will  }>< 
iro,.  from  it. 


ATTACK     ANH    IT.I'l  N<  B    OF    IT.IIMANT.NT    WuHKS. 

may  be  repeated  Beveral  nights  in  succession;  the  best  mo- 
ment  i>  just  before  dawn,  wheti  the  guards  of  the  trenches  are 
fatigued  and  sleepy  with  watching.  Although  the  chances  of 
success  are  greater  at  this  stage  than  at  the  opening  of  tin- 
trenches,  still,  it' the  besiegers  take  proper  precautions,  the  sor- 
tie will,  in  all  probability,  prove  more  prejudicial  than  advan- 
ous  t..  the  besieged, 

115... Before  the  besiegers  open  the  fire  of  the  enfilading 
batteries,  the  tire  of  the  defences  will  be  concentrated,  as  lias 
been  said,  on  the  principal  of  these,  and  will  he  kept  up 
against  them  until  a  marked  effect  is  observed  in  the  tire  of 
the  enfilading  batteries.  Only  one  gun  will  then  he  left  be- 
tween each  traverse  on  the  faces  of  the  defences,  the  others 
are  withdrawn  and  kept  in  reserve.  The  guns  and  howitzers 
kept  in  battery  will  fire  steadily  upon  the  heads  of  Che  ap- 
proaches as  they  are  gradually  advanced. 

116... After  the  third  parallel  is  constructed,  the  howitzers 
may  he  replaced,  with  advantage,  by  stone  and  Cochorri  mor- 
tars, firing  from  the  covered-ways  and  the  redoubts  of  the  re- 
entering  places  of  arms.  Guns  will  be  placed  in  embrasures, 
to  fire  in  the  direction  of  the  ditches  of  the  demilunes  of  at- 
tack against  the  crowning  of  their  covered-ways. 

117...  At  this  stage,  the  musketry  lire  of  the  besiegers  be- 
comes very  destructive  to  the  artillerists  whilst  serving  the 
gnns.  Strong  oak  musket-proof  blinds  should  be  arranged,  to 
mask  the  mouths  of  the  embrasures  when  the  guns  are  not  in 
battery.  Blinds,  or  covers  of  timber  and  earth,  under  which 
guns  can  lie  secured  from  projectiles  that  Would  reach  them  at 
top  or  in  flank,  will  now  be  serviceable.  A  few  guns  covered 
in  this  way,  and  placed  in  the  salients  of  the  collateral  works, 
to  obtain  a  reverse  view  on  the  trenches  constructed  on  the 
glacis,  will  prove  a  serious  annoyance  to  the  sappers,  and  will 
greatly  retard  their  progress. 

118. ..The  troops  in  the  covered-ways  will  keep  up  a  warm 
lire  of  musketry  against  the  heads  of  the  sap,  and  on  every  ex- 
posed   point.     The  men  firing  occupying  points   where   they 


ATTACK     AM)    I'M  PI. KM  \  \  I.NT    WOE  845 

will  be  best  sheltered  and  can  best  see  the  leading  sappers. 
A  few  marksmen,  will  also  occupy  the  parapets  of  the  demi- 
lunes and  the  redoubts,  to  keep  up  a  fire  from  them,  bnt  only 
during  tlic  daw  as  at  night  this  fire  might  Injure  the  men  in 
the  coveredjways. 

The  greater  part  of  the  guards  of  the  covered-way  should 
now  be  withdrawn   at  night,  and  be  posted  in  the  deniilu 
and  redoubts,  so  as  to  expose  but  few  troops  if  an  attack  by 
storm  is  made. 

119... Although  sorties  in  Large  bodies  will  seldom  provi 
cesst'ul  after  the  second  parallel  is  finished,  those  made  by  small 
detachments  of  1",  20  or  .".<»  men  against  the  head  of  a  sap,  of 
other  work,  when  tic  irs  are  advancing  beyond  the  third 

parallel,  will  seldom  fail  if  conducted  with  proper  precautions. 

This  method  of  annoyance  will  be  particularly  serviceable 
during  all  the  subsequent  Btages  of  the  defence,  as  the  bet 
ers  camot  now  have  at  hand  a  very  Large  force. 

120.. .The  defence  of  the  covered-ways  will  be  regulated  by 
the  method  pursued  in  the  attack.    When  the  Latter  is  made 
by  gradual  approaches,  the  troops,  with  the  exception  of  a  feu- 
men  who  can  find  a  shelter  behind  the  short  i  .  will  be 
withdrawn  from  the  salient  places  of  arms, 
ace  annoyed  l>y  the  fire  of  the  stone-mortars \  when  this  fire 
which  takes  place  when   the  sap  id  pushed  forward 
from  the  third  parallel — the  tro             tin  enter  the   salient 
places  of  arms,  and  renew  their  fire  on  the  heads  of  th< 
directing  it  particularly  against   the             -  working 
trench  cavaliers.     When  the  trench  oavalii  i 
and  armed,  the  troo                           om  the  sali<  d<  p 
arms,  and  occupy  the  tra 
maintain  their  fire,  and  throw  hand   grens 
it  comes  within  their                                     I 
also  placed  behind  th< 

121. ..If  the  to  be  mall  ira- 

fcions  to  attack  bv  storm,  no  a 
to  line  the  para; 
44 


** 


346  ATTACK   AND   DEFENCE    OF    PERMANENT    WoKKS. 

more  salient  parts,  and  they  should  maintain  their  position  no 
longer  than  is  necessary  to  give  th'e  storming  patty  one  volley 
as  they  debouch  from  the  third  parallel;  retreating  immedi- 
ately after  to  the  main  ditch,  or  to  other  designated  points. 
A  reserve  of  about  1(J0  men  is  posted  in  each  reentering  place 
of  arms,  to  cover  the  retreat  of  those  from  the  salients.  All 
the  other  outworks  are  lined  With  troops,  and  such  pieces  as 
can  still  be  brought  to  bear  on  the  glacis,  loaded  with  case 
shot,  open,  at  the  same  time  with  the  infantry,  a  deadly  lire 
on  the  storming  patty;  which  is  kept  up  until  the  assailants  are 
either  driven  from  the  covered-ways  or  take  shelter  in  the 
trenches  constructed  by  the  sappers  along  the  crest  of  the 
glacis.  A  vigorous  sortie,  botli  on  the  front,  the  flanks,  and 
the  rear  of  the  storming  [tarty,  made  from  the  collateral  cov- 
ered-ways, will,  in  such  cases,  be  a  judicious  operation. 

122. ..As  the  moment  for  crowning  the  covered-way  ap- 
proaches, the  efforts  of  the  besieged  will  be  redoubled  to  re- 
tard the  works  of  attack.  Independently  of  the  measures  al- 
ready laid  down,  the  besieged  will  arm  with  artillery  the  flanks 
which  bear  on  the  point  of  attack,  and  will  construct  oblique 
embrasures  in  the  curtains,  to  sweep  the  positions  along  the 
bastion  covered-ways,  where  the  besiegers  are  making  the 
breach  and  counter-batteries.  The  guards  of  the  covered-way 
will  retire  toward  the  reentering  as  the  crowning  of  the  cov- 
ered-way advances,  disputing  the  ground,  foot  by  foot,  and 
holding  possession  of  each  point  until  the  besiegers*are  nearly 
in  a  situation  to  envelop  it  with  their  works.  The  stone  and 
Coehorn  mortars  will  be  removed  to  the  reentering  places  of 
arms,  or  into  some  of  the  communications  in  the  rear  from 
which  a  fire  can  be  kept  up  on  the  trenches.  In  line,  every 
possible  means  will  be  resorted  to  by  which  the  sappers  con- 
structing the  breach  batteries  and  the  descents  can  be  cut  off* 
and  their  labors  be  retarded. 

123. ..When  the  besiegers  have  established  themselves  so 
strongly  on  the  glacis  and  the  covered-way  that  sorties  in  small 
parties  cannot  be  made  without  too  great  risk,  a  warm  fire  of 


ATTACK    AM)    DEFENCE    OF    PERMANENT    WORKS.  .".IT 

musketry  will  still  be  kept  up  od  the  trenches  from  all  the 
outworks,  and  the  besieged  will  wait  until  the  descent  of  the 
ditch  debouches  at  the  counterscarp  before  renewing  tin-  same 
game  of  sorties  in  small  parties.  A  vigilant  look-out  will  be 
kept,  to  ascertain  this  moment,  and  so  soon  as  tin  sappers  show 
themselves,  every  effort  will  Ik1  made  to  cut  them  off  and 
destroy  their  work,  by  opening  a  fire,  both  of  artillery  and 
musketry,  on  the  dchouehe,  by  sorties  in  small  bodies,  and  b\ 
throwing  loaded  shell.-,  grenades,  etc.,  into  the  ditch. 

124. ..In  wet  ditches,  filled  with  stagnant  water,  the  besieg<  d 
will  resort  frequently  to  night  attacks  in  boats  on  the  dike  or 
passage  ;  and,  in  the  case  where  water  can  he  suddenly  lei  into 
or  be  drawn  from  the  ditch,  chases  of  water  will  he  aged  to 
sweep  away  the  besieger's  works. 

KJ5...Irj  defending  the  breach  of  the  demilune,  the  besi 
will  resort,  not  only  to  the   lire  of  it.-   redoubt,  but    will    erect 
barricades  on  the  right  and  left  of  the  breach,  across  the  demi- 
lune terreplein,  from  which  a  warm  fire  of  musketry  will  be 
ponged  in  on  the  besiegers  whilst  they  attempt  to  gain  ]>"- 
sion  of  the  breach  either  by  gradual  approaches  or  by  storm. 
Small  mines,  or   bomb   fougasses,  should   be  prepared   at  the 
summit  of  the  bread].  t<>  be  exploded  .-■>  soon  as  the  I 
gain  possession  of  it.     Die  top  of  the  breach  will   be  strowti 
with   every  possible  obstacle  that   can  retard  the  progress  of 
the  storming  party,  and  grenades,  thundering-bari  .  will 

be  rolled  over  ou  the  troops  whilst  mounting  the  breach. 

L26...The  measures  for  the  defem t'  the  main  ditch  and  of 

the  breach  in   the  bastion  face,  differ1  in   nothing  from  t1 

rted  t<>  for  tin-  demilune.     Xhe  b  will  mal 

efforl  to  keep  possession  of  the  ditch  to  the  tn>t  moment,  b  • 
enpying  the   double  caponnii 
of  which  works  .'ire  will   h.  kept  tip 

whilst  effecting  the  p 
troops  will  be  frequently  made  nnder  Ui< 

by  the    lire  of  the    t<  nuh 

require  to  he  guarded   with  | 


348*  ATTACK    AND    DEFENCE    OF    l'KKMAM  NT    WORKS. 

besiegers  carrying  them  by  surprise,  and  thus  effecting  an  en- 
trance into  the  interior  of  the  work.  4 

1l'7...Aii  assault  of  the  breach  in  the  bastion  cannot  be  op- 
posed by  the  bayonet  without  compromising  the  lines  of  the 
garrison,  unless  there  exists  a  good  interior  retrenchment  to 
cover  the  retreat  from  the  breach  ;  even  in  this  case,  to  oppose 
the  storming  party  with  the  bayonet  will  be  an  operation  of 
great  delicacy,  for  the  besieged,  if  driven  back.'niav  not  be 
able  to  effect  their  retreat  without  being  so  mixed  up  with  the. 
assailants  as  to  render  it  impossible  to  prevent  the  latter  enter- 
ing with  them  into  the  retrenchments. 

128. ..Finally,  when  the  breach  is  effected  in  the  interior  re- 
trenchment, the  besieged  may  offer  to  capitulate,  unless  they 
are  still  able  to  protract  the  resistance  a  day  or  two  by  organ- 
izing temporary  defences,  and  by  placing  the  houses  u>  the 
rear  of  the  retrenchments  in  a  defensive  state,  in  which  cases 
this  breach  should  be  disputed  with  the  same  obstinacy  as 
those  of  the  other  works. 

RELATIVE    STRENGTH    OF   THE    GARRISON    AND 
BESIEGING   FORCE. 

As  a  permanent  work  should  force  "an  enemy  to  resort  to  an 
attack  by  regular  approaches,  its  garrison  should  be  at  least 
of  sufficient  strength  to  prevent  its  being  carried  by  a  coup  de 
main  or  open  assault.  The  largest  garrison  will  depend  upon 
the  means  provided  within  the  work  for  lodging  troops,  and 
securing  properly  the  munitions  of  war  requisite  for  the  num- 
ber that  can  be  accommodated  during  the  presumed  duration 
of  the  defence.  Between  these  two  limits  the  best  military 
authorities  estimate  as  a  medium  garrison,  capable  of  making 
a  good  defence,  000  men  per  front,  or  bastion  ;  this  force  being 
composed  of  the  different  arms  of  the  service  in  the  proper  pro- 
portions for  the  duties  required  of  them.  AVhen  the  defences 
comprise,  besides  the  enceinte,  some  of  the  principal  outworks, 
and  it  is  intended  to  occupy  them  strongly,  with  a  view  to  an 


ATTACK     AMMUMMT    01     I'KI.'MAMM     WOBK8.  349 

ttctive,  vigorous  defence,  an  allowance  from  900  to  L,< men 

should  lie  made  per  bastion. 

189..."With  rerfpect  to  the  quantity  of  artillery  necessary  for 
the  armament  of  a  permanent  work,  there  is  considerable  dis- 
crepancy 6f  opinion  among  military  writers.     A  resolute  gar- 
rison might  preserve  a  work  of  tolerable  strength  from  a  coup 
dc  main   without  the  aid   of  cannon;  and  an   idea  of  the 
largest  amount  of  artillery  might  be  arrived  at.  by   BUpp< 
each  front  to  lie  armed  with  as  many   pieces  a-  it   cdfo  carry, 
with  the  addition  of  a  suitable  number  of  pieces  in  reserye  to 
provide  for  casualties.     But   these  are  inadm 
and    a    medium    estimate    is   to   allow  ?,  heavy    guns   and 
heavy   mortar  per  front  or  hast  ion,  with   60  heavy  guns,  20 
heavy  •mortars  and    10   stone,  or  light  mortars,  for  the  arma- 
ment of  the  point  of  attack. 

In  estimating  the  amount  of  ammunition,  an  allowance  of 
1,000  rounds  is  made  for  each  j£un,  800  rounds  for  each  mor- 
tar, loo  musket  cartridges  per  day  for  each  soldier  <>n  guard  ; 
and  .".on  pounds  of  powder  for  each  mine. 

130.. .The  strength  of  the  besieging  force  is  baaed  upon  that 
of  tlie  garrison.    Hie  usr.nl  estimate  is  to  allow,  for  the  daily 
duty  of  the  trenches,  at  least  as  many  troops  a-  the  gavrif 
including  in  this  number  the  men  employed  in   making  the 
trenches.     As  the  service  of  the  b  ery  onerous,  the 

tour  of  duty  in  the  trenches  should  not  he  me re  fn  quent   than 
once  in  five  or  six  days.      Admitting  this  i 
ing  force,  comprising  all  arms,  should  he 
Btrong  a-  i!i.'  garrison. 

1  - *»  1 ...  1 1 1  estimating  tin-  quant  many 

guns  and  mdrtara  are  allowed  foi 
mortar  batteries  a-  tli.'  presumed  armament  i 

tack  ;   with  an  addition  . »1 
batt.  I 
The   medium   allowance  of  ammunition  for  tl 

1,000  rounds  tor  • 

L82...I1  i.-  hardly  i  • 


350  ATTACK   AND   DEFENCE   OF    PERMANENT    WORKS. 

mates  are  of  a  very  general  character,  and  are  introduced  here 
merely  to  give  some  idea  of  the  relative  proportions  in  ques- 
tion. Before  undertaking  the  siege  of  a  work,  no  pains  should 
be  spared  to  gain  all  the  information  possible  respecting  the 
state  of  its  defences,  and  the  probable  difficulties  to  be  encoun- 
tered in  i,ts  attack,  and  the  estimates  based  on  these  data 
should  be  made  on  the  supposition  of  the  work  being  provided 
with  all  the  means  of  a  vigorous  defence. 

Remarks.  In  the  preceding  description  of  the  methods  of 
attack  employed  against  permanent  fortifications,  the  calcula- 
tions for  the  extent  and  strength  of  the  trenches  and  batteries 
have  been  based  upon  the  range  and  effects  of  the  artillery 
and  small  arms  which  were  in  general  use  in  siege  operations 
up  to  the  recent  important  changes  and  improvements  which 
have  been  made  in  the  efficacy  of  arms  and  projectiles  of  every 
character.  What  corresponding  changes  in  the  methods  of 
attack  will  be  called  for,  arising  from  these  improvements, 
special  experiments  and  the  experience  derived  from  future 
sieges  can  alone  determine. 

From  the  very  ample  official  records  of  the  siege  of  Sebas- 
topol.  where  the  armament  of  the  defensive  works  consisted, 
in  a  great  measure,  of  the  heaviest  calibre  of  ships'  guns,  it 
would  seem  that  no  very  marked  deviations  were  made,  either 
by  the  French  or  English,  from  the  methods  of  attack  used  in 
previous  sieges.  The  first  parallels  were  commenced  at  about 
700  to  1,000  yards  from  the  positions  of  the  defences,  and  the 
trenches  were,  for  the  most  part,  executed  by  the  flying  sap; 
the  full  sap  being  used  by  the  French  sappers  alone,  and  only 
when  they  had  approached  very  near  to  the  defensive  'works. 
Owing  to  the  peculiar  difficulties  presented  by  the  character 
of  the  ground,  the  defensive  armor  prescribed  for  the  leading 
sappers  in  executing  the  full  sap  was  laid  aside  to  Enable  the 
men  to  work  more  effectively. 

In  the  construction  of  their  batteries,  the  French  appear  to 
have  deviated  only  in  exceptional  cases,  arising  from  the 
nature  of  the  site,  from  the     dimensions   and    constructions 


ATTACK   AND   DEFENCE    OF    PERMANENT    WORKS.  351 

which  had  beeD  previously  adopted  by  themi  The  English 
engineers,  from  their  experience  in  this  Biege,  are  in  favor  of 
thicker  parapets,  and  a  greater  exterrt  of'frontfor  each  gun  f<»r 
batteries,  particularly  for  the  heavy  calibres  of  ships'  guns 
with  which  Borne  of  their  batteries  were  armed.  These,  with 
a  few  minor  changes  in  the  details  of  platforms  and  emhra- 
sures,  are  the  only  modifications  in  the  Siege  works  of  any  im- 
portance which  the  results  of  this  memorable  si ■  .  a  to 
have  Suggested. 

In  the  defence  of  their  trenches  from  the  frequent  Borti(  - 
the  garrison,  the  French,  after  meeting  with  BeriOus  losses  in 
the  earlier  stages  of  the  Biege,  from  the  impetuosity  of  their1 
troops  in  Bally ing  upon  the  enemy  beyond   their   tren< 
finally  adopted  the  sale  rule  laid  down   by  Yauban   of  quietly 
withdrawing  the  guards  from  the  portion  tof  trenches  upon 
which  the  sortie  was  directed,  with  the  view  of  assailing  the 
enemy  so  soon  as  they  had   got  within    them   and  whilst  in  a 
confused  and  broken  condition.     This  plan   met  with  full   - 
and  was  found  most  effectual  in  restraining  thi 

In   their  defensive  works,  which  were  almost   entirely 
temporary  character,  the  Rue  Idopted  for  their  parapets 

the  ordinary  dimensions  for   resisting  the   1 

'Although    subjected    to   an    i no-  .--an t    and    terrible  lire   of  the 

heaviest  ships'  guns,  with  which  the 

armed,  these  parapets,  with  Buck  daily  care  as  could 

in  repairing  their  damagi  b,  Beem  to  ha>  e  afforded  am] 

to  the  garrison  from  the  direct  fire.     I  01 

fire,  resoii   was  had   to  blindages,  formed,  in 

nook,  with   the  heavy  timbers,  furnished  by  the  dock-ya 

which,  being  I  with   a  thii 

earth.   Beem    to   have   an- 

shelters  from  the  shocks  of  the  h< 
gunners  from  the  em 
sians  convert  d  the  h<  avy  rop<  --it1,' 
a  kind  of  matting,  w  hich  was,  in 

mouth  of  the  embra 


352  ATTACK   AM)   DEFENCE   OF   l'l'.UMANKXT    WOBKfi. 

made  of  a  circular  form,  with  a  hole  in  the  centre  large  enough 
to  admit  the  chase  of  the  gun,  to  which  it  was  fastened  as  a 

screen  for  the  men  at  the  trail. 

Owing  to  their  ani]>le  garrison,  the  Russians  were  enabled 
to  take  up  and  fortify  several  strong,  isolated  positions,  in  ad- 
vance of  their  continuous  line  of  works,  after  the  siege  opera- 
tions were  well  under  way.  They  also  nsed  with  great  advan- 
tage Btnall  troups-de-loup,oY  pits  for  sharp-shooters,  in  advance 
of  their  line,  from  which  both  the  workmen  at  the  trenches 
and  the  artillerists  of  the  besiegers  were  greatly  annoyed. 
These  were  in  some  cases  connected  and  formed  into  a  con- 
tinuous  trench  of  counter-approach,  from  which  they,  were  sub- 
sequently driven  only  after  considerable  loss  to  the  besiegers. 


> 


J>->  >:s>  ^»5s 


>>,•>    :>    •>  ';  i    >£T 

;V    -J?- ;' ^  v-r^iT  ,„ ->  ,      ;>>>  ■Ira*  JSa»>»V.i»     >  >Z>   >z>.j 

:*a  -sa     ■_::>"'■,  - ■■jCs?:>3»>o  :!>>>_^»^^^^  "  j^  :§>  .t^o  ■ 


1       -^     J#^-*  ^^''^^J^^^1 


J>^x3 


3^:3rtf 


J>  >A5ZJ*~^>i 


. 

JW       _ 

»^g*jb> 

2»  > 

-•»  >  _>.i>  >  >  > 

>   >'■ 

r> 

.'^>" 

S^5T3B>  5> ""; 

ja. 

"^>> 

■5^1»>    >>  > 

> 


>  ~>i~3>L. >    £>  "^> 


<5 


